diff --git a/doc/conf.py b/doc/conf.py
index 37b46b5e5..dcc403c67 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -26,20 +26,20 @@ import sys, os
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
 extensions = [
-    'sphinx.ext.intersphinx',
+    "sphinx.ext.intersphinx",
 ]
 
 # Add any paths that contain templates here, relative to this directory.
-templates_path = ['.templates']
+templates_path = [".templates"]
 
 # The suffix of source filenames.
-source_suffix = '.rst'
+source_suffix = ".rst"
 
 # The encoding of source files.
 #source_encoding = 'utf-8-sig'
 
 # The master toctree document.
-master_doc = 'index'
+master_doc = "index"
 
 # General information about the project.
 project = u'Modoboa'
@@ -50,9 +50,9 @@ copyright = u'2018, Antoine Nguyen'
 # built documents.
 #
 # The short X.Y version.
-version = '1.10'
+version = "1.10"
 # The full version, including alpha/beta/rc tags.
-release = '1.10.0'
+release = "1.10.0"
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
@@ -66,7 +66,7 @@ release = '1.10.0'
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
-exclude_patterns = ['.build']
+exclude_patterns = [".build"]
 
 # The reST default role (used for this markup: `text`) to use for all documents.
 #default_role = None
@@ -83,7 +83,7 @@ exclude_patterns = ['.build']
 #show_authors = False
 
 # The name of the Pygments (syntax highlighting) style to use.
-pygments_style = 'sphinx'
+pygments_style = "sphinx"
 
 # A list of ignored prefixes for module index sorting.
 #modindex_common_prefix = []
@@ -94,11 +94,11 @@ pygments_style = 'sphinx'
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
 
-on_rtd = os.environ.get('READTHEDOCS', None) == 'True'
+on_rtd = os.environ.get("READTHEDOCS", None) == "True"
 if on_rtd:
-    html_theme = 'default'
+    html_theme = "default"
 else:
-    html_theme = 'nature'
+    html_theme = "nature"
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the
@@ -127,7 +127,7 @@ else:
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = ['_static']
+html_static_path = ["_static"]
 
 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.
@@ -171,7 +171,7 @@ html_static_path = ['_static']
 #html_file_suffix = None
 
 # Output file base name for HTML help builder.
-htmlhelp_basename = 'Modoboadoc'
+htmlhelp_basename = "Modoboadoc"
 
 
 # -- Options for LaTeX output --------------------------------------------------
@@ -185,8 +185,8 @@ htmlhelp_basename = 'Modoboadoc'
 # Grouping the document tree into LaTeX files. List of tuples
 # (source start file, target name, title, author, documentclass [howto/manual]).
 latex_documents = [
-  ('index', 'Modoboa.tex', u'Modoboa Documentation',
-   u'Antoine Nguyen', 'manual'),
+  ("index", "Modoboa.tex", u'Modoboa Documentation',
+   u'Antoine Nguyen', "manual"),
 ]
 
 # The name of an image file (relative to this directory) to place at the top of
@@ -218,10 +218,10 @@ latex_documents = [
 # One entry per manual page. List of tuples
 # (source start file, name, description, authors, manual section).
 man_pages = [
-    ('index', 'modoboa', u'Modoboa Documentation',
+    ("index", "modoboa", u'Modoboa Documentation',
      [u'Antoine Nguyen'], 1)
 ]
 
 intersphinx_mapping = {
-    'amavis': ('http://modoboa-amavis.readthedocs.org/en/latest/', None)
+    "amavis": ("http://modoboa-amavis.readthedocs.org/en/latest/", None)
 }
diff --git a/modoboa/admin/api.py b/modoboa/admin/api.py
index a0e91e439..4afb9065a 100644
--- a/modoboa/admin/api.py
+++ b/modoboa/admin/api.py
@@ -81,7 +81,7 @@ class AccountViewSet(viewsets.ModelViewSet):
         user = self.request.user
         ids = user.objectaccess_set \
             .filter(content_type=ContentType.objects.get_for_model(user)) \
-            .values_list('object_id', flat=True)
+            .values_list("object_id", flat=True)
         queryset = core_models.User.objects.filter(pk__in=ids)
         domain = self.request.query_params.get("domain")
         if domain:
@@ -139,7 +139,7 @@ class AliasViewSet(viewsets.ModelViewSet):
         ids = (
             user.objectaccess_set.filter(
                 content_type=ContentType.objects.get_for_model(models.Alias))
-            .values_list('object_id', flat=True)
+            .values_list("object_id", flat=True)
         )
         queryset = models.Alias.objects.filter(pk__in=ids)
         domain = self.request.query_params.get("domain")
diff --git a/modoboa/admin/factories.py b/modoboa/admin/factories.py
index b62ba877a..3f9b3f26c 100644
--- a/modoboa/admin/factories.py
+++ b/modoboa/admin/factories.py
@@ -79,44 +79,44 @@ def populate_database():
     """
     dom = DomainFactory(name="test.com", quota=50)
     admin = UserFactory(
-        username="admin@test.com", groups=('DomainAdmins', ),
-        password='{PLAIN}toto'
+        username="admin@test.com", groups=("DomainAdmins", ),
+        password="{PLAIN}toto"
     )
-    MailboxFactory(address='admin', domain=dom, user=admin)
+    MailboxFactory(address="admin", domain=dom, user=admin)
     account = UserFactory.create(
-        username="user@test.com", groups=('SimpleUsers',),
+        username="user@test.com", groups=("SimpleUsers",),
     )
-    MailboxFactory.create(address='user', domain=dom, user=account)
+    MailboxFactory.create(address="user", domain=dom, user=account)
 
     al = AliasFactory.create(
-        address='forward@test.com', domain=dom
+        address="forward@test.com", domain=dom
     )
     AliasRecipientFactory.create(
-        address='user@external.com', alias=al)
+        address="user@external.com", alias=al)
 
     al = AliasFactory.create(
-        address='alias@test.com', domain=dom
+        address="alias@test.com", domain=dom
     )
     mb = account.mailbox
     AliasRecipientFactory.create(
         address=mb.full_address, alias=al, r_mailbox=mb)
 
     al = AliasFactory.create(
-        address='postmaster@test.com', domain=dom
+        address="postmaster@test.com", domain=dom
     )
-    for address in ['toto@titi.com', 'test@truc.fr']:
+    for address in ["toto@titi.com", "test@truc.fr"]:
         AliasRecipientFactory.create(address=address, alias=al)
 
     dom.add_admin(admin)
 
-    dom2 = DomainFactory.create(name='test2.com', default_mailbox_quota=0)
+    dom2 = DomainFactory.create(name="test2.com", default_mailbox_quota=0)
     admin = UserFactory.create(
-        username='admin@test2.com', groups=('DomainAdmins',),
-        password='{PLAIN}toto'
+        username="admin@test2.com", groups=("DomainAdmins",),
+        password="{PLAIN}toto"
     )
-    MailboxFactory.create(address='admin', domain=dom2, user=admin)
+    MailboxFactory.create(address="admin", domain=dom2, user=admin)
     u = UserFactory.create(
-        username='user@test2.com', groups=('SimpleUsers',)
+        username="user@test2.com", groups=("SimpleUsers",)
     )
-    MailboxFactory.create(address='user', domain=dom2, user=u)
+    MailboxFactory.create(address="user", domain=dom2, user=u)
     dom2.add_admin(admin)
diff --git a/modoboa/admin/forms/__init__.py b/modoboa/admin/forms/__init__.py
index b7811a0d9..263ea5808 100644
--- a/modoboa/admin/forms/__init__.py
+++ b/modoboa/admin/forms/__init__.py
@@ -13,9 +13,9 @@ from .import_ import ImportDataForm, ImportIdentitiesForm
 from .export import ExportDataForm, ExportDomainsForm, ExportIdentitiesForm
 
 __all__ = [
-    'DomainFormGeneral', 'DomainFormOptions', 'DomainForm',
-    'AccountFormGeneral', 'AccountFormMail', 'AccountPermissionsForm',
-    'AccountForm', 'AliasForm', 'ImportDataForm', 'ImportIdentitiesForm',
-    'ExportDataForm', 'ExportDomainsForm', 'ExportIdentitiesForm',
-    'ForwardForm', 'DomainWizard', 'AccountWizard'
+    "DomainFormGeneral", "DomainFormOptions", "DomainForm",
+    "AccountFormGeneral", "AccountFormMail", "AccountPermissionsForm",
+    "AccountForm", "AliasForm", "ImportDataForm", "ImportIdentitiesForm",
+    "ExportDataForm", "ExportDomainsForm", "ExportIdentitiesForm",
+    "ForwardForm", "DomainWizard", "AccountWizard"
 ]
diff --git a/modoboa/admin/forms/account.py b/modoboa/admin/forms/account.py
index 1622a8f62..a2987fa8c 100644
--- a/modoboa/admin/forms/account.py
+++ b/modoboa/admin/forms/account.py
@@ -527,9 +527,9 @@ class AccountForm(TabForms):
     def extra_context(self, context):
         account = self.instances["general"]
         context.update({
-            'title': account.username,
-            'formid': 'accountform',
-            'action': reverse("admin:account_change",
+            "title": account.username,
+            "formid": "accountform",
+            "action": reverse("admin:account_change",
                               args=[account.id]),
         })
 
@@ -604,9 +604,9 @@ class AccountWizard(WizardForm):
 
     def extra_context(self, context):
         context.update({
-            'title': _("New account"),
-            'action': reverse("admin:account_add"),
-            'formid': 'newaccount_form'
+            "title": _("New account"),
+            "action": reverse("admin:account_add"),
+            "formid": "newaccount_form"
         })
 
     def done(self):
diff --git a/modoboa/admin/forms/domain.py b/modoboa/admin/forms/domain.py
index ddd4bf070..7b2a0ce69 100644
--- a/modoboa/admin/forms/domain.py
+++ b/modoboa/admin/forms/domain.py
@@ -82,7 +82,7 @@ class DomainFormGeneral(forms.ModelForm, DynamicForm):
         """Check unicity and more."""
         name = self.cleaned_data["name"]
         label = lib.check_if_domain_exists(
-            name, [(DomainAlias, _('domain alias'))])
+            name, [(DomainAlias, _("domain alias"))])
         if label is not None:
             raise forms.ValidationError(
                 _("A %s with this name already exists") % force_text(label))
diff --git a/modoboa/admin/handlers.py b/modoboa/admin/handlers.py
index a91a12667..bc673e85a 100644
--- a/modoboa/admin/handlers.py
+++ b/modoboa/admin/handlers.py
@@ -161,7 +161,7 @@ def account_auto_created(sender, user, **kwargs):
     if not param_tools.get_global_parameter("auto_create_domain_and_mailbox"):
         return
     localpart, domname = split_mailbox(user.username)
-    if user.role != 'SimpleUsers' and domname is None:
+    if user.role != "SimpleUsers" and domname is None:
         return
     sadmins = core_models.User.objects.filter(is_superuser=True)
     try:
diff --git a/modoboa/admin/lib.py b/modoboa/admin/lib.py
index e85ca33cc..f2541946d 100644
--- a/modoboa/admin/lib.py
+++ b/modoboa/admin/lib.py
@@ -59,7 +59,7 @@ def get_identities(user, searchquery=None, idtfilter=None, grpfilter=None):
     if idtfilter is None or not idtfilter or idtfilter == "account":
         ids = user.objectaccess_set \
             .filter(content_type=ContentType.objects.get_for_model(user)) \
-            .values_list('object_id', flat=True)
+            .values_list("object_id", flat=True)
         q = Q(pk__in=ids)
         if searchquery is not None:
             q &= Q(username__icontains=searchquery) \
@@ -76,7 +76,7 @@ def get_identities(user, searchquery=None, idtfilter=None, grpfilter=None):
             or (idtfilter in ["alias", "forward", "dlist"]):
         alct = ContentType.objects.get_for_model(Alias)
         ids = user.objectaccess_set.filter(content_type=alct) \
-            .values_list('object_id', flat=True)
+            .values_list("object_id", flat=True)
         q = Q(pk__in=ids, internal=False)
         if searchquery is not None:
             q &= (
diff --git a/modoboa/admin/management/commands/handle_mailbox_operations.py b/modoboa/admin/management/commands/handle_mailbox_operations.py
index 8888cb9eb..a5f86613d 100644
--- a/modoboa/admin/management/commands/handle_mailbox_operations.py
+++ b/modoboa/admin/management/commands/handle_mailbox_operations.py
@@ -80,7 +80,7 @@ class Command(BaseCommand):
             )
             if not code:
                 return False
-        with open(path, 'w') as fp:
+        with open(path, "w") as fp:
             print(os.getpid(), file=fp)
         return True
 
diff --git a/modoboa/admin/management/commands/subcommands/_export.py b/modoboa/admin/management/commands/subcommands/_export.py
index bad0e0afd..ed53b8026 100644
--- a/modoboa/admin/management/commands/subcommands/_export.py
+++ b/modoboa/admin/management/commands/subcommands/_export.py
@@ -46,12 +46,12 @@ class ExportCommand(BaseCommand):
             dumped_aliases += [alias.pk]
         qset = (
             models.Alias.objects.exclude(pk__in=dumped_aliases)
-            .prefetch_related('aliasrecipient_set')
+            .prefetch_related("aliasrecipient_set")
         )
         for alias in qset:
             alias.to_csv(self.csvwriter)
 
     def handle(self, *args, **options):
         exts_pool.load_all()
-        self.csvwriter = csv.writer(sys.stdout, delimiter=options['sepchar'])
+        self.csvwriter = csv.writer(sys.stdout, delimiter=options["sepchar"])
         getattr(self, "export_{}".format(options["objtype"]))()
diff --git a/modoboa/admin/management/commands/subcommands/_import.py b/modoboa/admin/management/commands/subcommands/_import.py
index 1c9c16d89..80e3a6ad5 100644
--- a/modoboa/admin/management/commands/subcommands/_import.py
+++ b/modoboa/admin/management/commands/subcommands/_import.py
@@ -30,7 +30,7 @@ class ImportCommand(BaseCommand):
             help="Separator used in file.")
         parser.add_argument(
             "--continue-if-exists", action="store_true",
-            dest='continue_if_exists', default=False,
+            dest="continue_if_exists", default=False,
             help="Continue even if an entry already exists.")
         parser.add_argument(
             "--crypt-password", action="store_true",
diff --git a/modoboa/admin/models/alias.py b/modoboa/admin/models/alias.py
index 225ed9e78..b689eb841 100644
--- a/modoboa/admin/models/alias.py
+++ b/modoboa/admin/models/alias.py
@@ -48,7 +48,7 @@ class Alias(AdminObject):
         ugettext_lazy("Description"), blank=True)
     expire_at = models.DateTimeField(
         ugettext_lazy("Expire at"), blank=True, null=True)
-    _objectname = 'MailboxAlias'
+    _objectname = "MailboxAlias"
 
     class Meta:
         permissions = (
@@ -139,7 +139,7 @@ class Alias(AdminObject):
                     domain=domain, address=local_part).first()
                 if rcpt is None:
                     rcpt = Alias.objects.filter(
-                        address='%s@%s' % (local_part, domname)
+                        address="%s@%s" % (local_part, domname)
                     ).first()
                     if rcpt is None:
                         raise NotFound(
diff --git a/modoboa/admin/models/domain.py b/modoboa/admin/models/domain.py
index fa0337a3a..ff2c72f27 100644
--- a/modoboa/admin/models/domain.py
+++ b/modoboa/admin/models/domain.py
@@ -27,7 +27,7 @@ from .. import constants
 class Domain(AdminObject):
     """Mail domain."""
 
-    name = models.CharField(ugettext_lazy('name'), max_length=100, unique=True,
+    name = models.CharField(ugettext_lazy("name"), max_length=100, unique=True,
                             help_text=ugettext_lazy("The domain name"))
     quota = models.PositiveIntegerField(
         default=0,
@@ -45,7 +45,7 @@ class Domain(AdminObject):
         )
     )
     enabled = models.BooleanField(
-        ugettext_lazy('enabled'),
+        ugettext_lazy("enabled"),
         help_text=ugettext_lazy("Check to activate this domain"),
         default=True
     )
diff --git a/modoboa/admin/models/domain_alias.py b/modoboa/admin/models/domain_alias.py
index 51ccfba69..508e3a91c 100644
--- a/modoboa/admin/models/domain_alias.py
+++ b/modoboa/admin/models/domain_alias.py
@@ -39,12 +39,12 @@ class DomainAlias(AdminObject):
     name = models.CharField(ugettext_lazy("name"), max_length=100, unique=True,
                             help_text=ugettext_lazy("The alias name"))
     target = models.ForeignKey(
-        Domain, verbose_name=ugettext_lazy('target'),
+        Domain, verbose_name=ugettext_lazy("target"),
         help_text=ugettext_lazy("The domain this alias points to"),
         on_delete=models.CASCADE
     )
     enabled = models.BooleanField(
-        ugettext_lazy('enabled'),
+        ugettext_lazy("enabled"),
         help_text=ugettext_lazy("Check to activate this alias"),
         default=True
     )
diff --git a/modoboa/admin/models/mailbox.py b/modoboa/admin/models/mailbox.py
index d32005959..278cc41c9 100644
--- a/modoboa/admin/models/mailbox.py
+++ b/modoboa/admin/models/mailbox.py
@@ -66,9 +66,9 @@ class MailboxManager(Manager):
         """
         qf = None
         if squery is not None:
-            if '@' in squery:
-                parts = squery.split('@')
-                addrfilter = '@'.join(parts[:-1])
+            if "@" in squery:
+                parts = squery.split("@")
+                addrfilter = "@".join(parts[:-1])
                 domfilter = parts[-1]
                 qf = (
                     Q(address__contains=addrfilter) &
@@ -81,7 +81,7 @@ class MailboxManager(Manager):
                 )
         ids = admin.objectaccess_set \
             .filter(content_type=ContentType.objects.get_for_model(Mailbox)) \
-            .values_list('object_id', flat=True)
+            .values_list("object_id", flat=True)
         if qf is not None:
             qf = Q(pk__in=ids) & qf
         else:
@@ -94,7 +94,7 @@ class Mailbox(AdminObject):
     """User mailbox."""
 
     address = models.CharField(
-        ugettext_lazy('address'), max_length=252,
+        ugettext_lazy("address"), max_length=252,
         help_text=ugettext_lazy(
             "Mailbox address (without the @domain.tld part)")
     )
@@ -376,7 +376,7 @@ class MailboxOperation(models.Model):
     mailbox = models.ForeignKey(Mailbox, blank=True, null=True,
                                 on_delete=models.CASCADE)
     type = models.CharField(
-        max_length=20, choices=(('rename', 'rename'), ('delete', 'delete'))
+        max_length=20, choices=(("rename", "rename"), ("delete", "delete"))
     )
     argument = models.TextField()
 
@@ -384,6 +384,6 @@ class MailboxOperation(models.Model):
         app_label = "admin"
 
     def __str__(self):
-        if self.type == 'rename':
-            return 'Rename %s -> %s' % (self.argument, self.mailbox.mail_home)
-        return 'Delete %s' % self.argument
+        if self.type == "rename":
+            return "Rename %s -> %s" % (self.argument, self.mailbox.mail_home)
+        return "Delete %s" % self.argument
diff --git a/modoboa/admin/postfix_maps.py b/modoboa/admin/postfix_maps.py
index c904a7eeb..373500154 100644
--- a/modoboa/admin/postfix_maps.py
+++ b/modoboa/admin/postfix_maps.py
@@ -7,7 +7,7 @@ class DomainsMap(object):
 
     """Map to list all domains."""
 
-    filename = 'sql-domains.cf'
+    filename = "sql-domains.cf"
     mysql = (
         "SELECT name FROM admin_domain "
         "WHERE name='%s' AND type='domain' AND enabled=1"
@@ -26,7 +26,7 @@ class DomainsAliasesMap(object):
 
     """Map to list all domain aliases."""
 
-    filename = 'sql-domain-aliases.cf'
+    filename = "sql-domain-aliases.cf"
     mysql = (
         "SELECT dom.name FROM admin_domain dom "
         "INNER JOIN admin_domainalias domal ON dom.id=domal.target_id "
@@ -48,7 +48,7 @@ class AliasesMap(object):
 
     """A map to list all mailbox aliases."""
 
-    filename = 'sql-aliases.cf'
+    filename = "sql-aliases.cf"
     mysql = (
         "SELECT alr.address FROM modoboa_admin_aliasrecipient AS alr "
         "INNER JOIN admin_alias AS al ON alr.alias_id=al.id "
@@ -73,7 +73,7 @@ class MaintainMap(object):
 
     """Map files to list non available mailboxes."""
 
-    filename = 'sql-maintain.cf'
+    filename = "sql-maintain.cf"
     mysql = (
         "SELECT '450 Requested mail action not taken: mailbox unavailable' "
         "FROM admin_mailbox mb INNER JOIN admin_domain dom "
diff --git a/modoboa/admin/templatetags/admin_tags.py b/modoboa/admin/templatetags/admin_tags.py
index 202088157..7f0601230 100644
--- a/modoboa/admin/templatetags/admin_tags.py
+++ b/modoboa/admin/templatetags/admin_tags.py
@@ -75,7 +75,7 @@ def domains_menu(selection, user, ajax_mode=True):
              "modalcb": "admin.exportform_cb"}
         ]
 
-    return render_to_string('common/menulist.html', {
+    return render_to_string("common/menulist.html", {
         "entries": entries,
         "selection": selection,
         "user": user
@@ -123,7 +123,7 @@ def identities_menu(user, selection=None, ajax_mode=True):
          "modalcb": "admin.exportform_cb"}
     ]
 
-    return render_to_string('common/menulist.html', {
+    return render_to_string("common/menulist.html", {
         "entries": entries,
         "user": user
     })
@@ -229,15 +229,15 @@ def domain_aliases(domain):
     :rtype: str
     """
     if not domain.aliases.count():
-        return '---'
-    res = ''
+        return "---"
+    res = ""
     for alias in domain.aliases.all():
-        res += '%s<br/>' % alias.name
+        res += "%s<br/>" % alias.name
     return mark_safe(res)
 
 
 @register.simple_tag
-def identity_modify_link(identity, active_tab='default'):
+def identity_modify_link(identity, active_tab="default"):
     """Return the appropriate modification link.
 
     According to the identity type, a specific modification link (URL)
diff --git a/modoboa/admin/tests/test_account.py b/modoboa/admin/tests/test_account.py
index cddbe6297..1428c3d47 100644
--- a/modoboa/admin/tests/test_account.py
+++ b/modoboa/admin/tests/test_account.py
@@ -28,7 +28,7 @@ class AuthenticationTestCase(ModoTestCase):
         cls.mb = factories.MailboxFactory(
             domain__name="test.com", address="user",
             user__username="user@test.com",
-            user__groups=('SimpleUsers',)
+            user__groups=("SimpleUsers",)
         )
 
     def test_authentication_unicode(self):
@@ -56,7 +56,7 @@ class AccountTestCase(ModoTestCase):
             username="tester@test.com", first_name="Tester", last_name="Toto",
             password1="Toto1234", password2="Toto1234", role="SimpleUsers",
             quota_act=True,
-            is_active=True, email="tester@test.com", stepid='step2'
+            is_active=True, email="tester@test.com", stepid="step2"
         )
         self.ajax_post(reverse("admin:account_add"), values)
 
@@ -459,8 +459,8 @@ class AccountTestCase(ModoTestCase):
 
 @skipIf(NO_LDAP, "No ldap module installed")
 @override_settings(AUTHENTICATION_BACKENDS=(
-    'modoboa.lib.authbackends.LDAPBackend',
-    'django.contrib.auth.backends.ModelBackend',
+    "modoboa.lib.authbackends.LDAPBackend",
+    "django.contrib.auth.backends.ModelBackend",
 ))
 class LDAPAccountTestCase(test_ldap.LDAPTestCaseMixin, ModoTestCase):
     """Check LDAP related code."""
@@ -597,7 +597,7 @@ class PermissionsTestCase(ModoTestCase):
 
         response = self.client.get(
             reverse("admin:account_change", args=[self.user.id]),
-            HTTP_X_REQUESTED_WITH='XMLHttpRequest')
+            HTTP_X_REQUESTED_WITH="XMLHttpRequest")
         self.assertNotEqual(response["Content-Type"], "application/json")
 
     def test_domainadmin_deletes_superadmin(self):
@@ -611,7 +611,7 @@ class PermissionsTestCase(ModoTestCase):
             username="superadmin2@test.com", first_name="Super",
             last_name="Admin", password1="Toto1234", password2="Toto1234",
             role="SuperAdmins", is_active=True,
-            email="superadmin2@test.com", stepid='step2'
+            email="superadmin2@test.com", stepid="step2"
         )
         self.ajax_post(
             reverse("admin:account_add"),
@@ -641,7 +641,7 @@ class PermissionsTestCase(ModoTestCase):
             username="user10@test.com", first_name="Test",
             last_name="Test", password1="Toto1234", password2="Toto1234",
             role="SimpleUsers", is_active=True, master_user=True,
-            email="user10@test.com", stepid='step2'
+            email="user10@test.com", stepid="step2"
         )
         self.ajax_post(
             reverse("admin:account_add"),
@@ -656,7 +656,7 @@ class PermissionsTestCase(ModoTestCase):
         dom = models.Domain.objects.get(name="test.com")
         mb = factories.MailboxFactory(
             domain=dom, address="admin2",
-            user__username="admin2@test.com", user__groups=('DomainAdmins', ),
+            user__username="admin2@test.com", user__groups=("DomainAdmins", ),
             user__password="{PLAIN}toto")
         dom.add_admin(mb.user)
         self.client.logout()
diff --git a/modoboa/admin/tests/test_api.py b/modoboa/admin/tests/test_api.py
index bd5c2582c..060ef940d 100644
--- a/modoboa/admin/tests/test_api.py
+++ b/modoboa/admin/tests/test_api.py
@@ -69,7 +69,7 @@ class DomainAPITestCase(ModoAPITestCase):
         self.assertIn("default_mailbox_quota", response.data)
 
         self.client.credentials(
-            HTTP_AUTHORIZATION='Token ' + self.da_token.key)
+            HTTP_AUTHORIZATION="Token " + self.da_token.key)
         response = self.client.post(
             url, {"name": "test4.com", "default_mailbox_quota": 10})
         self.assertEqual(response.status_code, 403)
@@ -84,7 +84,7 @@ class DomainAPITestCase(ModoAPITestCase):
         reseller = core_factories.UserFactory(
             username="reseller", groups=("Resellers", ))
         token = Token.objects.create(user=reseller)
-        self.client.credentials(HTTP_AUTHORIZATION='Token ' + token.key)
+        self.client.credentials(HTTP_AUTHORIZATION="Token " + token.key)
 
         url = reverse("api:domain-list")
         mock_query.side_effect = utils.mock_dns_query_result
@@ -169,7 +169,7 @@ class DomainAliasAPITestCase(ModoAPITestCase):
         self.assertEqual(len(response.data), 1)
 
         self.client.credentials(
-            HTTP_AUTHORIZATION='Token ' + self.da_token.key)
+            HTTP_AUTHORIZATION="Token " + self.da_token.key)
         response = self.client.get(reverse("api:domain_alias-list"))
         self.assertEqual(response.status_code, 200)
         self.assertEqual(len(response.data), 0)
@@ -191,7 +191,7 @@ class DomainAliasAPITestCase(ModoAPITestCase):
         self.assertEqual(dalias.target, target)
 
         self.client.credentials(
-            HTTP_AUTHORIZATION='Token ' + self.da_token.key)
+            HTTP_AUTHORIZATION="Token " + self.da_token.key)
         response = self.client.post(
             url, {"name": "dalias4.com", "target": target.pk}, format="json")
         self.assertEqual(response.status_code, 403)
@@ -389,7 +389,7 @@ class AccountAPITestCase(ModoAPITestCase):
     def test_create_account_as_domadmin(self):
         """As DomainAdmin, try to create a new account."""
         self.client.credentials(
-            HTTP_AUTHORIZATION='Token ' + self.da_token.key)
+            HTTP_AUTHORIZATION="Token " + self.da_token.key)
         data = copy.deepcopy(self.ACCOUNT_DATA)
         data["mailbox"]["quota"] = 1000
         url = reverse("api:account-list")
@@ -604,7 +604,7 @@ class AliasAPITestCase(ModoAPITestCase):
         response = self.client.post(url, self.ALIAS_DATA, format="json")
         self.assertEqual(response.status_code, 201)
 
-        alias = json.loads(response.content.decode('utf-8'))
+        alias = json.loads(response.content.decode("utf-8"))
         alias = models.Alias.objects.filter(pk=alias["pk"]).first()
         domadmin = core_models.User.objects.get(username="admin@test.com")
         self.assertTrue(domadmin.can_access(alias))
@@ -626,7 +626,7 @@ class AliasAPITestCase(ModoAPITestCase):
     def test_create_alias_as_domadmin(self):
         """As DomainAdmin, try to create a new alias."""
         self.client.credentials(
-            HTTP_AUTHORIZATION='Token ' + self.da_token.key)
+            HTTP_AUTHORIZATION="Token " + self.da_token.key)
         url = reverse("api:alias-list")
         response = self.client.post(url, self.ALIAS_DATA, format="json")
         self.assertEqual(response.status_code, 201)
@@ -723,7 +723,7 @@ class SenderAddressAPITestCase(ModoAPITestCase):
         self.assertEqual(response.status_code, 201)
 
         self.client.credentials(
-            HTTP_AUTHORIZATION='Token ' + self.da_token.key)
+            HTTP_AUTHORIZATION="Token " + self.da_token.key)
         data = {"address": "user@test2.com", "mailbox": mbox.pk}
         response = self.client.post(url, data)
         self.assertEqual(response.status_code, 400)
diff --git a/modoboa/admin/tests/test_domain.py b/modoboa/admin/tests/test_domain.py
index cabab25e3..f009a8609 100644
--- a/modoboa/admin/tests/test_domain.py
+++ b/modoboa/admin/tests/test_domain.py
@@ -176,7 +176,7 @@ class DomainTestCase(ModoTestCase):
         values = {
             "name": "pouet.com", "quota": 10, "default_mailbox_quota": 100,
             "create_dom_admin": True, "dom_admin_username": "toto",
-            "create_aliases": True, "type": "domain", "stepid": 'step3'
+            "create_aliases": True, "type": "domain", "stepid": "step3"
         }
         response = self.ajax_post(
             reverse("admin:domain_add"),
@@ -347,13 +347,13 @@ class DomainTestCase(ModoTestCase):
         url = reverse("core:dashboard")
         response = self.client.get(url)
         self.assertEqual(response.status_code, 200)
-        self.assertIn("Global statistics", response.content.decode('utf-8'))
+        self.assertIn("Global statistics", response.content.decode("utf-8"))
 
         self.client.force_login(
             User.objects.get(username="admin@test.com"))
         response = self.client.get(url)
         self.assertEqual(response.status_code, 200)
-        content = response.content.decode('utf-8')
+        content = response.content.decode("utf-8")
         self.assertNotIn("Global statistics", content)
         self.assertIn("Per-domain statistics", content)
 
diff --git a/modoboa/admin/tests/test_domain_alias.py b/modoboa/admin/tests/test_domain_alias.py
index 5dd667702..4c11bb7d7 100644
--- a/modoboa/admin/tests/test_domain_alias.py
+++ b/modoboa/admin/tests/test_domain_alias.py
@@ -17,7 +17,7 @@ class DomainAliasTestCase(ModoTestCase):
         """Create test data."""
         super(DomainAliasTestCase, cls).setUpTestData()
         factories.populate_database()
-        cls.dom = Domain.objects.get(name='test.com')
+        cls.dom = Domain.objects.get(name="test.com")
 
     def test_model(self):
         dom = Domain.objects.get(name="test.com")
diff --git a/modoboa/admin/tests/test_import_.py b/modoboa/admin/tests/test_import_.py
index cfe9f7317..a11dcef8a 100644
--- a/modoboa/admin/tests/test_import_.py
+++ b/modoboa/admin/tests/test_import_.py
@@ -217,7 +217,7 @@ account; user1@test.com; toto; User; One; True; SimpleUsers; user1@test.com; ; t
             reverse("admin:identity_import"),
             {"sourcefile": f, "crypt_password": True}
         )
-        self.assertIn('wrong quota value', resp.content.decode())
+        self.assertIn("wrong quota value", resp.content.decode())
 
     def test_import_domain_by_domainadmin(self):
         """Check if a domain admin is not allowed to import a domain."""
diff --git a/modoboa/admin/tests/test_password_schemes.py b/modoboa/admin/tests/test_password_schemes.py
index 277d202b9..99392ccef 100644
--- a/modoboa/admin/tests/test_password_schemes.py
+++ b/modoboa/admin/tests/test_password_schemes.py
@@ -21,7 +21,7 @@ class PasswordSchemesTestCase(ModoTestCase):
             username="tester@test.com", first_name="Tester", last_name="Toto",
             password1="Toto1234", password2="Toto1234", role="SimpleUsers",
             quota_act=True,
-            is_active=True, email="tester@test.com", stepid='step2'
+            is_active=True, email="tester@test.com", stepid="step2"
         )
         self.ajax_post(
             reverse("admin:account_add"),
@@ -31,30 +31,30 @@ class PasswordSchemesTestCase(ModoTestCase):
     def _test_scheme(self, name, startpattern):
         self.set_global_parameter("password_scheme", name, app="core")
         self._create_account()
-        account = User.objects.get(username='tester@test.com')
+        account = User.objects.get(username="tester@test.com")
         self.assertTrue(account.password.startswith(startpattern))
-        self.assertTrue(account.check_password('Toto1234'))
+        self.assertTrue(account.check_password("Toto1234"))
 
     def test_bcrypt_scheme(self):
-        self._test_scheme('blfcrypt', '{BLF-CRYPT}')
+        self._test_scheme("blfcrypt", "{BLF-CRYPT}")
 
     def test_sha512crypt_scheme(self):
-        self._test_scheme('sha512crypt', '{SHA512-CRYPT}')
+        self._test_scheme("sha512crypt", "{SHA512-CRYPT}")
 
     def test_sha256crypt_scheme(self):
-        self._test_scheme('sha256crypt', '{SHA256-CRYPT}')
+        self._test_scheme("sha256crypt", "{SHA256-CRYPT}")
 
     def test_md5crypt_scheme(self):
-        self._test_scheme('md5crypt', '{MD5-CRYPT}')
+        self._test_scheme("md5crypt", "{MD5-CRYPT}")
 
     def test_sha256_scheme(self):
-        self._test_scheme('sha256', '{SHA256}')
+        self._test_scheme("sha256", "{SHA256}")
 
     def test_md5_scheme(self):
-        self._test_scheme('md5', '{MD5}')
+        self._test_scheme("md5", "{MD5}")
 
     def test_crypt(self):
-        self._test_scheme('crypt', '{CRYPT}')
+        self._test_scheme("crypt", "{CRYPT}")
 
     def test_plain(self):
-        self._test_scheme('plain', '{PLAIN}')
+        self._test_scheme("plain", "{PLAIN}")
diff --git a/modoboa/admin/tests/test_repair.py b/modoboa/admin/tests/test_repair.py
index e3e3b67ef..623892ce8 100644
--- a/modoboa/admin/tests/test_repair.py
+++ b/modoboa/admin/tests/test_repair.py
@@ -49,7 +49,7 @@ class RepairTestCase(ModoTestCase):
 
     def test_management_command_with_nul_domain(self):
         """Just assume nothing raise when an alias has no domain."""
-        models.Alias.objects.create(address='@modoboa.xxx')
+        models.Alias.objects.create(address="@modoboa.xxx")
         ret = management.call_command("modo", "repair", "--quiet")
         assert ret is None
 
diff --git a/modoboa/admin/urls.py b/modoboa/admin/urls.py
index eff6fc2bb..3a9e2c38f 100644
--- a/modoboa/admin/urls.py
+++ b/modoboa/admin/urls.py
@@ -27,7 +27,7 @@ urlpatterns = [
         name="domain_quota_list"),
     url(r'^domains/flatlist/$', domain_views.domains_list,
         name="domain_flat_list"),
-    url(r'^domains/new/', domain_views.newdomain, name='domain_add'),
+    url(r'^domains/new/', domain_views.newdomain, name="domain_add"),
     url(r'^domains/(?P<dom_id>\d+)/edit/$', domain_views.editdomain,
         name="domain_change"),
     url(r'^domains/(?P<dom_id>\d+)/delete/$', domain_views.deldomain,
diff --git a/modoboa/admin/views/alias.py b/modoboa/admin/views/alias.py
index a7c97f58b..5a4151df2 100644
--- a/modoboa/admin/views/alias.py
+++ b/modoboa/admin/views/alias.py
@@ -37,7 +37,7 @@ def _validate_alias(request, form, successmsg, callback=None):
             callback(request.user, alias)
         return render_to_json_response(successmsg)
 
-    return render_to_json_response({'form_errors': form.errors}, status=400)
+    return render_to_json_response({"form_errors": form.errors}, status=400)
 
 
 def _new_alias(request, title, action, successmsg,
@@ -87,12 +87,12 @@ def editalias(request, alid, tplname="admin/aliasform.html"):
         return _validate_alias(request, form, successmsg)
 
     ctx = {
-        'action': reverse("admin:alias_change", args=[alias.id]),
-        'formid': 'aliasform',
-        'title': alias.address,
-        'action_label': _('Update'),
-        'action_classes': 'submit',
-        'form': AliasForm(request.user, instance=alias)
+        "action": reverse("admin:alias_change", args=[alias.id]),
+        "formid": "aliasform",
+        "title": alias.address,
+        "action_label": _("Update"),
+        "action_classes": "submit",
+        "form": AliasForm(request.user, instance=alias)
     }
     return render(request, tplname, ctx)
 
diff --git a/modoboa/admin/views/domain.py b/modoboa/admin/views/domain.py
index 4618b294a..e0b970d5a 100644
--- a/modoboa/admin/views/domain.py
+++ b/modoboa/admin/views/domain.py
@@ -51,16 +51,16 @@ def _domains(request):
         (flt, request.GET.get(flt, None))
         for flt in ["domfilter", "searchquery"] + extra_filters
     )
-    request.session['domains_filters'] = filters
+    request.session["domains_filters"] = filters
     domainlist = get_domains(request.user, **filters)
-    if sort_order == 'name':
+    if sort_order == "name":
         domainlist = sorted(
             domainlist,
-            key=lambda d: getattr(d, sort_order), reverse=sort_dir == '-'
+            key=lambda d: getattr(d, sort_order), reverse=sort_dir == "-"
         )
     else:
         domainlist = sorted(domainlist, key=lambda d: d.tags[0]["name"],
-                            reverse=sort_dir == '-')
+                            reverse=sort_dir == "-")
     context = {
         "handle_mailboxes": request.localconfig.parameters.get_value(
             "handle_mailboxes", raise_exception=False),
diff --git a/modoboa/admin/views/export.py b/modoboa/admin/views/export.py
index a2d82e79e..8cbfa4af8 100644
--- a/modoboa/admin/views/export.py
+++ b/modoboa/admin/views/export.py
@@ -52,7 +52,7 @@ def export_identities(request):
         fp = six.StringIO()
         csvwriter = csv.writer(fp, delimiter=form.cleaned_data["sepchar"])
         identities = get_identities(
-            request.user, **request.session['identities_filters'])
+            request.user, **request.session["identities_filters"])
         for ident in identities:
             ident.to_csv(csvwriter)
         content = fp.getvalue()
@@ -80,7 +80,7 @@ def export_domains(request):
         fp = six.StringIO()
         csvwriter = csv.writer(fp, delimiter=form.cleaned_data["sepchar"])
         for dom in get_domains(request.user,
-                               **request.session['domains_filters']):
+                               **request.session["domains_filters"]):
             dom.to_csv(csvwriter)
         content = fp.getvalue()
         fp.close()
diff --git a/modoboa/admin/views/identity.py b/modoboa/admin/views/identity.py
index 669a49b62..4f3ba61ab 100644
--- a/modoboa/admin/views/identity.py
+++ b/modoboa/admin/views/identity.py
@@ -37,17 +37,17 @@ from .. import signals
 )
 def _identities(request):
     filters = dict((fname, request.GET.get(fname, None))
-                   for fname in ['searchquery', 'idtfilter', 'grpfilter'])
-    request.session['identities_filters'] = filters
+                   for fname in ["searchquery", "idtfilter", "grpfilter"])
+    request.session["identities_filters"] = filters
     idents_list = get_identities(request.user, **filters)
     sort_order, sort_dir = get_sort_order(request.GET, "identity",
                                           ["identity", "name_or_rcpt", "tags"])
     if sort_order in ["identity", "name_or_rcpt"]:
         objects = sorted(idents_list, key=lambda o: getattr(o, sort_order),
-                         reverse=sort_dir == '-')
+                         reverse=sort_dir == "-")
     else:
         objects = sorted(idents_list, key=lambda o: o.tags[0],
-                         reverse=sort_dir == '-')
+                         reverse=sort_dir == "-")
     context = {
         "handle_mailboxes": request.localconfig.parameters.get_value(
             "handle_mailboxes", raise_exception=False)
@@ -104,7 +104,7 @@ def list_quotas(request):
                     "* 1048576)) * 100"
                 )
             mboxes = mboxes.extra(
-                select={'quota_usage': select},
+                select={"quota_usage": select},
                 where=["admin_quota.username=%s" % where],
                 tables=["admin_quota", "admin_domain"],
                 order_by=["%s%s" % (sort_dir, sort_order)]
@@ -157,7 +157,7 @@ def identities(request, tplname="admin/identities.html"):
 @permission_required("core.add_user")
 def accounts_list(request):
     accs = User.objects.filter(is_superuser=False) \
-        .exclude(groups__name='SimpleUsers')
+        .exclude(groups__name="SimpleUsers")
     res = [a.username for a in accs.all()]
     return render_to_json_response(res)
 
diff --git a/modoboa/admin/views/import_.py b/modoboa/admin/views/import_.py
index e63a4e849..e05e858b1 100644
--- a/modoboa/admin/views/import_.py
+++ b/modoboa/admin/views/import_.py
@@ -39,8 +39,8 @@ def importdata(request, formclass=ImportDataForm):
     if form.is_valid():
         try:
             infile = io.TextIOWrapper(
-                request.FILES['sourcefile'].file, encoding="utf8")
-            reader = csv.reader(infile, delimiter=form.cleaned_data['sepchar'])
+                request.FILES["sourcefile"].file, encoding="utf8")
+            reader = csv.reader(infile, delimiter=form.cleaned_data["sepchar"])
         except csv.Error as inst:
             error = smart_text(inst)
         else:
@@ -63,7 +63,7 @@ def importdata(request, formclass=ImportDataForm):
                                 continue
                             raise Conflict(
                                 _("Object already exists: %s"
-                                  % form.cleaned_data['sepchar'].join(row[:2]))
+                                  % form.cleaned_data["sepchar"].join(row[:2]))
                             )
                     cpt += 1
                 msg = _("%d objects imported successfully" % cpt)
diff --git a/modoboa/admin/views/user.py b/modoboa/admin/views/user.py
index 424111919..072f68890 100644
--- a/modoboa/admin/views/user.py
+++ b/modoboa/admin/views/user.py
@@ -40,7 +40,7 @@ def forward(request, tplname="admin/forward.html"):
             return render_to_json_response(_("Forward updated"))
 
         return render_to_json_response(
-            {'form_errors': form.errors}, status=400
+            {"form_errors": form.errors}, status=400
         )
 
     form = ForwardForm()
diff --git a/modoboa/core/app_settings.py b/modoboa/core/app_settings.py
index 8934c9773..8be3c572a 100644
--- a/modoboa/core/app_settings.py
+++ b/modoboa/core/app_settings.py
@@ -40,8 +40,8 @@ class GeneralParametersForm(param_forms.AdminParametersForm):
 
     authentication_type = forms.ChoiceField(
         label=ugettext_lazy("Authentication type"),
-        choices=[('local', ugettext_lazy("Local")),
-                 ('ldap', "LDAP")],
+        choices=[("local", ugettext_lazy("Local")),
+                 ("ldap", "LDAP")],
         initial="local",
         help_text=ugettext_lazy("The backend used for authentication"),
         widget=HorizontalRadioSelect()
@@ -115,16 +115,16 @@ class GeneralParametersForm(param_forms.AdminParametersForm):
 
     ldap_auth_method = forms.ChoiceField(
         label=ugettext_lazy("Authentication method"),
-        choices=[('searchbind', ugettext_lazy("Search and bind")),
-                 ('directbind', ugettext_lazy("Direct bind"))],
-        initial='searchbind',
+        choices=[("searchbind", ugettext_lazy("Search and bind")),
+                 ("directbind", ugettext_lazy("Direct bind"))],
+        initial="searchbind",
         help_text=ugettext_lazy("Choose the authentication method to use"),
         widget=forms.Select(attrs={"class": "form-control"})
     )
 
     ldap_bind_dn = forms.CharField(
         label=ugettext_lazy("Bind DN"),
-        initial='',
+        initial="",
         help_text=ugettext_lazy(
             "The distinguished name to use when binding to the LDAP server. "
             "Leave empty for an anonymous bind"
@@ -135,7 +135,7 @@ class GeneralParametersForm(param_forms.AdminParametersForm):
 
     ldap_bind_password = forms.CharField(
         label=ugettext_lazy("Bind password"),
-        initial='',
+        initial="",
         help_text=ugettext_lazy(
             "The password to use when binding to the LDAP server "
             "(with 'Bind DN')"
diff --git a/modoboa/core/commands/__init__.py b/modoboa/core/commands/__init__.py
index f21b36fa7..6a25852a6 100644
--- a/modoboa/core/commands/__init__.py
+++ b/modoboa/core/commands/__init__.py
@@ -90,10 +90,10 @@ def handle_command_line():
         epilog="""Available commands:
 %s
 """ % "\n".join(["\t%s" % c for c in sorted(commands)]))
-    parser.add_argument('--verbose', action='store_true',
-                        help='Activate verbose output')
-    parser.add_argument('command', type=str,
-                        help='A valid command name')
+    parser.add_argument("--verbose", action="store_true",
+                        help="Activate verbose output")
+    parser.add_argument("command", type=str,
+                        help="A valid command name")
     (args, remaining) = parser.parse_known_args()
 
     if args.command not in commands:
diff --git a/modoboa/core/commands/deploy.py b/modoboa/core/commands/deploy.py
index 11f079f2f..959b9c12b 100644
--- a/modoboa/core/commands/deploy.py
+++ b/modoboa/core/commands/deploy.py
@@ -58,40 +58,40 @@ class DeployCommand(Command):
 
     def __init__(self, *args, **kwargs):
         super(DeployCommand, self).__init__(*args, **kwargs)
-        self._parser.add_argument('name', type=str,
-                                  help='The name of your Modoboa instance')
+        self._parser.add_argument("name", type=str,
+                                  help="The name of your Modoboa instance")
         self._parser.add_argument(
-            '--collectstatic', action='store_true', default=False,
-            help='Run django collectstatic command'
+            "--collectstatic", action="store_true", default=False,
+            help="Run django collectstatic command"
         )
         self._parser.add_argument(
-            '--dburl', type=str, nargs="+", default=None,
-            help='A database-url with a name')
+            "--dburl", type=str, nargs="+", default=None,
+            help="A database-url with a name")
         self._parser.add_argument(
-            '--domain', type=str, default=None,
-            help='The domain under which you want to deploy modoboa')
+            "--domain", type=str, default=None,
+            help="The domain under which you want to deploy modoboa")
         self._parser.add_argument(
-            '--lang', type=str, default="en-us",
+            "--lang", type=str, default="en-us",
             help="Set the default language"
         )
         self._parser.add_argument(
-            '--timezone', type=str, default="UTC",
+            "--timezone", type=str, default="UTC",
             help="Set the local timezone"
         )
         self._parser.add_argument(
-            '--devel', action='store_true', default=False,
-            help='Create a development instance'
+            "--devel", action="store_true", default=False,
+            help="Create a development instance"
         )
         self._parser.add_argument(
-            '--extensions', type=str, nargs='*',
+            "--extensions", type=str, nargs="*",
             help="The list of extension to deploy"
         )
         self._parser.add_argument(
-            '--dont-install-extensions', action='store_true', default=False,
-            help='Do not install extensions using pip'
+            "--dont-install-extensions", action="store_true", default=False,
+            help="Do not install extensions using pip"
         )
         self._parser.add_argument(
-            '--admin-username', default='admin',
+            "--admin-username", default="admin",
             help="Username of the initial super administrator"
         )
 
@@ -101,7 +101,7 @@ class DeployCommand(Command):
         :param name: the command name
         :param cwd: the directory where the command must be executed
         """
-        cmd = [sys.executable, 'manage.py', name]
+        cmd = [sys.executable, "manage.py", name]
         cmd.extend(args)
         if not self._verbose:
             p = subprocess.Popen(
@@ -120,7 +120,7 @@ class DeployCommand(Command):
                 )
             print("%s failed, check your configuration" % cmd, file=sys.stderr)
 
-    def ask_db_info(self, name='default'):
+    def ask_db_info(self, name="default"):
         """Prompt the user for database information
 
         Gather all information required to create a new database
@@ -130,33 +130,33 @@ class DeployCommand(Command):
         """
         print("Configuring database connection: %s" % name)
         info = {
-            'conn_name': name,
-            'ENGINE': input(
-                'Database type (mysql, postgres or sqlite3): ')
+            "conn_name": name,
+            "ENGINE": input(
+                "Database type (mysql, postgres or sqlite3): ")
         }
-        if info['ENGINE'] not in ['mysql', 'postgres', 'sqlite3']:
-            raise RuntimeError('Unsupported database engine')
+        if info["ENGINE"] not in ["mysql", "postgres", "sqlite3"]:
+            raise RuntimeError("Unsupported database engine")
 
-        if info['ENGINE'] == 'sqlite3':
-            info['ENGINE'] = 'django.db.backends.sqlite3'
-            info['NAME'] = '%s.db' % name
+        if info["ENGINE"] == "sqlite3":
+            info["ENGINE"] = "django.db.backends.sqlite3"
+            info["NAME"] = "%s.db" % name
             return info
-        if info['ENGINE'] == 'postgres':
-            info['ENGINE'] = 'django.db.backends.postgresql_psycopg2'
+        if info["ENGINE"] == "postgres":
+            info["ENGINE"] = "django.db.backends.postgresql_psycopg2"
             default_port = 5432
         else:
-            info['ENGINE'] = 'django.db.backends.mysql'
+            info["ENGINE"] = "django.db.backends.mysql"
             default_port = 3306
-        info['HOST'] = input("Database host (default: 'localhost'): ")
-        info['PORT'] = input(
+        info["HOST"] = input("Database host (default: 'localhost'): ")
+        info["PORT"] = input(
             "Database port (default: '%s'): " % default_port)
         # leave port setting empty, if default value is supplied and
         # leave it to django
-        if info['PORT'] == default_port:
-            info['PORT'] = ''
-        info['NAME'] = input('Database name: ')
-        info['USER'] = input('Username: ')
-        info['PASSWORD'] = getpass.getpass('Password: ')
+        if info["PORT"] == default_port:
+            info["PORT"] = ""
+        info["NAME"] = input("Database name: ")
+        info["USER"] = input("Username: ")
+        info["PASSWORD"] = getpass.getpass("Password: ")
         return info
 
     def _get_extension_list(self):
@@ -188,9 +188,9 @@ class DeployCommand(Command):
     def handle(self, parsed_args):
         django.setup()
         management.call_command(
-            'startproject', parsed_args.name, verbosity=False
+            "startproject", parsed_args.name, verbosity=False
         )
-        path = "%(name)s/%(name)s" % {'name': parsed_args.name}
+        path = "%(name)s/%(name)s" % {"name": parsed_args.name}
         sys.path.append(parsed_args.name)
 
         conn_tpl = Template(DBCONN_TPL)
@@ -206,7 +206,7 @@ class DeployCommand(Command):
                     info = self.ask_db_info(conn_name)
                 # If we set this earlier, our fallback method will never
                 # be triggered
-                info['conn_name'] = conn_name
+                info["conn_name"] = conn_name
                 connections[conn_name] = conn_tpl.render(Context(info))
         else:
             connections["default"] = conn_tpl.render(
@@ -216,7 +216,7 @@ class DeployCommand(Command):
             allowed_host = parsed_args.domain
         else:
             allowed_host = input(
-                'What will be the hostname used to access Modoboa? ')
+                "What will be the hostname used to access Modoboa? ")
             if not allowed_host:
                 allowed_host = "localhost"
         extra_settings = []
@@ -238,20 +238,20 @@ class DeployCommand(Command):
         )
 
         mod = __import__(
-            parsed_args.name, globals(), locals(), [smart_str('settings')]
+            parsed_args.name, globals(), locals(), [smart_str("settings")]
         )
         tpl = self._render_template(
             "%s/settings.py.tpl" % self._templates_dir, {
-                'db_connections': connections,
-                'secret_key': mod.settings.SECRET_KEY,
-                'name': parsed_args.name,
-                'allowed_host': allowed_host,
-                'lang': parsed_args.lang,
-                'timezone': parsed_args.timezone,
-                'bower_components_dir': bower_components_dir,
-                'devmode': parsed_args.devel,
-                'extensions': extensions,
-                'extra_settings': extra_settings
+                "db_connections": connections,
+                "secret_key": mod.settings.SECRET_KEY,
+                "name": parsed_args.name,
+                "allowed_host": allowed_host,
+                "lang": parsed_args.lang,
+                "timezone": parsed_args.timezone,
+                "bower_components_dir": bower_components_dir,
+                "devmode": parsed_args.devel,
+                "extensions": extensions,
+                "extra_settings": extra_settings
             }
         )
         with codecs.open("%s/settings.py" % path, "w", "utf-8") as fp:
@@ -264,7 +264,7 @@ class DeployCommand(Command):
         if isfile("%s/settings.pyc" % path):
             os.unlink("%s/settings.pyc" % path)
         self._exec_django_command(
-            "migrate", parsed_args.name, '--noinput'
+            "migrate", parsed_args.name, "--noinput"
         )
         self._exec_django_command(
             "load_initial_data", parsed_args.name,
@@ -272,7 +272,7 @@ class DeployCommand(Command):
         )
         if parsed_args.collectstatic:
             self._exec_django_command(
-                "collectstatic", parsed_args.name, '--noinput'
+                "collectstatic", parsed_args.name, "--noinput"
             )
         self._exec_django_command(
             "set_default_site", parsed_args.name, allowed_host
diff --git a/modoboa/core/commands/help.py b/modoboa/core/commands/help.py
index 88c7efc0b..d7257bc03 100644
--- a/modoboa/core/commands/help.py
+++ b/modoboa/core/commands/help.py
@@ -13,8 +13,8 @@ class HelpCommand(Command):
 
     def __init__(self, *args, **kwargs):
         super(HelpCommand, self).__init__(*args, **kwargs)
-        self._parser.add_argument('name', type=str,
-                                  help='A command name')
+        self._parser.add_argument("name", type=str,
+                                  help="A command name")
 
     def handle(self, parsed_args):
         if parsed_args.name not in self._commands:
diff --git a/modoboa/core/extensions.py b/modoboa/core/extensions.py
index a6ea04909..79323e1d1 100644
--- a/modoboa/core/extensions.py
+++ b/modoboa/core/extensions.py
@@ -79,7 +79,7 @@ class ExtensionsPool(object):
 
     def load_extension(self, name):
         """Load a registered extension."""
-        __import__(name, locals(), globals(), [smart_str('modo_extension')])
+        __import__(name, locals(), globals(), [smart_str("modo_extension")])
         extinstance = self.get_extension(name)
         if extinstance is None:
             return None
diff --git a/modoboa/core/models.py b/modoboa/core/models.py
index c3e7c0a74..39c9e7d42 100644
--- a/modoboa/core/models.py
+++ b/modoboa/core/models.py
@@ -83,7 +83,7 @@ class User(AbstractUser):
     class Meta(object):
         ordering = ["username"]
         index_together = [
-            ['email', 'is_active']
+            ["email", "is_active"]
         ]
 
     password_expr = re.compile(r'\{([\w\-]+)\}(.+)')
@@ -412,7 +412,7 @@ class ObjectAccess(models.Model):
     user = models.ForeignKey(User, on_delete=models.CASCADE)
     content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
     object_id = models.PositiveIntegerField()
-    content_object = GenericForeignKey('content_type', 'object_id')
+    content_object = GenericForeignKey("content_type", "object_id")
     is_owner = models.BooleanField(default=False)
 
     class Meta(object):
diff --git a/modoboa/core/password_hashers/__init__.py b/modoboa/core/password_hashers/__init__.py
index 6269c666c..e47231f1f 100644
--- a/modoboa/core/password_hashers/__init__.py
+++ b/modoboa/core/password_hashers/__init__.py
@@ -22,8 +22,8 @@ def get_password_hasher(scheme):
     :return: The hasher class
     """
     try:
-        scheme = scheme.replace('-', '')
-        hasher = globals()['%sHasher' % scheme.upper()]
+        scheme = scheme.replace("-", "")
+        hasher = globals()["%sHasher" % scheme.upper()]
     except KeyError:
         hasher = PLAINHasher
     return hasher
diff --git a/modoboa/core/password_hashers/advanced.py b/modoboa/core/password_hashers/advanced.py
index 0f526221c..1ab654b26 100644
--- a/modoboa/core/password_hashers/advanced.py
+++ b/modoboa/core/password_hashers/advanced.py
@@ -22,7 +22,7 @@ class BLFCRYPTHasher(PasswordHasher):
     """
     @property
     def scheme(self):
-        return '{BLF-CRYPT}' if self._target == 'local' else '{CRYPT}'
+        return "{BLF-CRYPT}" if self._target == "local" else "{CRYPT}"
 
     def _b64encode(self, pwhash):
         return pwhash
@@ -50,7 +50,7 @@ class MD5CRYPTHasher(PasswordHasher):
     """
     @property
     def scheme(self):
-        return '{MD5-CRYPT}' if self._target == 'local' else '{CRYPT}'
+        return "{MD5-CRYPT}" if self._target == "local" else "{CRYPT}"
 
     def _b64encode(self, pwhash):
         return pwhash
@@ -72,7 +72,7 @@ class SHA256CRYPTHasher(PasswordHasher):
     """
     @property
     def scheme(self):
-        return '{SHA256-CRYPT}' if self._target == 'local' else '{CRYPT}'
+        return "{SHA256-CRYPT}" if self._target == "local" else "{CRYPT}"
 
     def _b64encode(self, pwhash):
         return pwhash
@@ -96,7 +96,7 @@ class SHA512CRYPTHasher(PasswordHasher):
     """
     @property
     def scheme(self):
-        return '{SHA512-CRYPT}' if self._target == 'local' else '{CRYPT}'
+        return "{SHA512-CRYPT}" if self._target == "local" else "{CRYPT}"
 
     def _b64encode(self, pwhash):
         return pwhash
diff --git a/modoboa/core/password_hashers/base.py b/modoboa/core/password_hashers/base.py
index a449c8088..59f8d7a64 100644
--- a/modoboa/core/password_hashers/base.py
+++ b/modoboa/core/password_hashers/base.py
@@ -22,7 +22,7 @@ class PasswordHasher(object):
     Base class of all hashers.
     """
 
-    def __init__(self, target='local'):
+    def __init__(self, target="local"):
         self._target = target
 
     def _encrypt(self, clearvalue, salt=None):
@@ -34,7 +34,7 @@ class PasswordHasher(object):
         :param str pwhash: password hash
         :return: base64 encoded hash or original hash
         """
-        if self._target == 'ldap':
+        if self._target == "ldap":
             return base64.b64encode(pwhash)
         return pwhash
 
@@ -52,7 +52,7 @@ class PasswordHasher(object):
         :return: encrypted password
         """
         pwhash = self._b64encode(self._encrypt(force_text(clearvalue)))
-        return '%s%s' % (self.scheme, force_text(pwhash))
+        return "%s%s" % (self.scheme, force_text(pwhash))
 
     def verify(self, clearvalue, hashed_value):
         """Verify a password against a hashed value.
@@ -74,7 +74,7 @@ class PLAINHasher(PasswordHasher):
     """
     @property
     def scheme(self):
-        return '{PLAIN}'
+        return "{PLAIN}"
 
     def _encrypt(self, clearvalue, salt=None):
         return clearvalue
@@ -89,7 +89,7 @@ class CRYPTHasher(PasswordHasher):
     """
     @property
     def scheme(self):
-        return '{CRYPT}'
+        return "{CRYPT}"
 
     def _encrypt(self, clearvalue, salt=None):
         if salt is None:
@@ -106,7 +106,7 @@ class MD5Hasher(PasswordHasher):
     """
     @property
     def scheme(self):
-        return '{MD5}'
+        return "{MD5}"
 
     def _encrypt(self, clearvalue, salt=None):
         obj = hashlib.md5(force_bytes(clearvalue))
@@ -122,7 +122,7 @@ class SHA256Hasher(PasswordHasher):
     """
     @property
     def scheme(self):
-        return '{SHA256}'
+        return "{SHA256}"
 
     def _encrypt(self, clearvalue, salt=None):
         return hashlib.sha256(force_bytes(clearvalue)).digest()
diff --git a/modoboa/core/templatetags/core_tags.py b/modoboa/core/templatetags/core_tags.py
index 25ef503af..ce6a3b2bc 100644
--- a/modoboa/core/templatetags/core_tags.py
+++ b/modoboa/core/templatetags/core_tags.py
@@ -72,7 +72,7 @@ def admin_menu(selection, user):
          "img": "",
          "label": _("Parameters")},
     ]
-    return render_to_string('common/menu.html', {
+    return render_to_string("common/menu.html", {
         "entries": entries,
         "css": "nav nav-sidebar",
         "selection": selection,
@@ -163,7 +163,7 @@ def tohtml(message):
 
 @register.simple_tag
 def visirule(field):
-    if not hasattr(field, 'form') or \
+    if not hasattr(field, "form") or \
             not hasattr(field.form, "visirules") or \
             field.html_name not in field.form.visirules:
         return ""
@@ -191,7 +191,7 @@ class ConnectedUsers(template.Node):
         # Build a list of user ids from that query
         for session in sessions:
             data = session.get_decoded()
-            uid = data.get('_auth_user_id', None)
+            uid = data.get("_auth_user_id", None)
             if uid:
                 uid_list.append(uid)
 
@@ -202,7 +202,7 @@ class ConnectedUsers(template.Node):
                 context[self.varname].append(User.objects.get(pk=uid))
             except User.DoesNotExist:
                 pass
-        return ''
+        return ""
 
 
 @register.tag
@@ -211,7 +211,7 @@ def connected_users(parser, token):
         tag, a, varname = token.split_contents()
     except ValueError:
         raise template.TemplateSyntaxError(
-            'connected_users usage: {% connected_users as users %}'
+            "connected_users usage: {% connected_users as users %}"
         )
     return ConnectedUsers(varname)
 
diff --git a/modoboa/core/tests/test_authentication.py b/modoboa/core/tests/test_authentication.py
index 08c7fb4dc..93581e3f7 100644
--- a/modoboa/core/tests/test_authentication.py
+++ b/modoboa/core/tests/test_authentication.py
@@ -28,7 +28,7 @@ class AuthenticationTestCase(ModoTestCase):
         """Create test data."""
         super(AuthenticationTestCase, cls).setUpTestData()
         cls.account = factories.UserFactory(
-            username="user@test.com", groups=('SimpleUsers',)
+            username="user@test.com", groups=("SimpleUsers",)
         )
 
     def test_authentication(self):
@@ -75,10 +75,10 @@ class PasswordResetTestCase(ModoTestCase):
         super(PasswordResetTestCase, cls).setUpTestData()
         cls.account_ok = factories.UserFactory(
             username="user@test.com", secondary_email="test@ext.com",
-            groups=('SimpleUsers',)
+            groups=("SimpleUsers",)
         )
         cls.account_ko = factories.UserFactory(
-            username="user2@test.com", groups=('SimpleUsers',)
+            username="user2@test.com", groups=("SimpleUsers",)
         )
 
     def test_reset_password(self):
@@ -104,7 +104,7 @@ class PasswordResetTestCase(ModoTestCase):
         self.assertEqual(len(mail.outbox), 0)
 
 
-@skipIf(NO_SMTP, 'No SMTP server available')
+@skipIf(NO_SMTP, "No SMTP server available")
 @override_settings(AUTHENTICATION_BACKENDS=(
     "modoboa.lib.authbackends.SMTPBackend",
     "django.contrib.auth.backends.ModelBackend"
diff --git a/modoboa/core/tests/test_core.py b/modoboa/core/tests/test_core.py
index 73ffa4b11..0e39f633d 100644
--- a/modoboa/core/tests/test_core.py
+++ b/modoboa/core/tests/test_core.py
@@ -28,7 +28,7 @@ class AuthenticationTestCase(ModoTestCase):
         """Create test data."""
         super(AuthenticationTestCase, cls).setUpTestData()
         cls.account = factories.UserFactory(
-            username="user@test.com", groups=('SimpleUsers',)
+            username="user@test.com", groups=("SimpleUsers",)
         )
 
     def test_authentication(self):
@@ -109,7 +109,7 @@ class ProfileTestCase(ModoTestCase):
         """Create test data."""
         super(ProfileTestCase, cls).setUpTestData()
         cls.account = factories.UserFactory(
-            username="user@test.com", groups=('SimpleUsers',)
+            username="user@test.com", groups=("SimpleUsers",)
         )
 
     def test_update_profile(self):
@@ -168,7 +168,7 @@ class APIAccessFormTestCase(ModoTestCase):
         """Create test data."""
         super(APIAccessFormTestCase, cls).setUpTestData()
         cls.account = factories.UserFactory(
-            username="user@test.com", groups=('SimpleUsers',)
+            username="user@test.com", groups=("SimpleUsers",)
         )
 
     def test_form_access(self):
diff --git a/modoboa/core/tests/test_ldap.py b/modoboa/core/tests/test_ldap.py
index 2de9be271..5b2a19631 100644
--- a/modoboa/core/tests/test_ldap.py
+++ b/modoboa/core/tests/test_ldap.py
@@ -16,7 +16,7 @@ from .. import factories
 from .. import models
 
 
-@skipIf(NO_LDAP, 'No ldap module installed')
+@skipIf(NO_LDAP, "No ldap module installed")
 class LDAPTestCaseMixin(object):
     """Set of methods used to test LDAP features."""
 
@@ -71,8 +71,8 @@ class LDAPTestCaseMixin(object):
 
 
 @override_settings(AUTHENTICATION_BACKENDS=(
-    'modoboa.lib.authbackends.LDAPBackend',
-    'django.contrib.auth.backends.ModelBackend'
+    "modoboa.lib.authbackends.LDAPBackend",
+    "django.contrib.auth.backends.ModelBackend"
 ))
 class LDAPAuthenticationTestCase(LDAPTestCaseMixin, ModoTestCase):
     """Validate LDAP authentication scenarios."""
@@ -137,12 +137,12 @@ class ProfileTestCase(LDAPTestCaseMixin, ModoTestCase):
         """Create test data."""
         super(ProfileTestCase, cls).setUpTestData()
         cls.account = factories.UserFactory(
-            username="user@test.com", groups=('SimpleUsers',)
+            username="user@test.com", groups=("SimpleUsers",)
         )
 
     @override_settings(AUTHENTICATION_BACKENDS=(
-        'modoboa.lib.authbackends.LDAPBackend',
-        'django.contrib.auth.backends.ModelBackend'
+        "modoboa.lib.authbackends.LDAPBackend",
+        "django.contrib.auth.backends.ModelBackend"
     ))
     def test_update_password_ldap(self):
         """Update password for an LDAP user."""
diff --git a/modoboa/core/tests/test_views.py b/modoboa/core/tests/test_views.py
index c9d5a004a..dcb2047d8 100644
--- a/modoboa/core/tests/test_views.py
+++ b/modoboa/core/tests/test_views.py
@@ -108,12 +108,12 @@ class DashboardTestCase(ModoTestCase):
         url = reverse("core:dashboard")
         response = self.client.get(url)
         self.assertEqual(response.status_code, 200)
-        self.assertIn("Latest news", response.content.decode('utf-8'))
+        self.assertIn("Latest news", response.content.decode("utf-8"))
         self.client.logout()
         self.client.login(username=self.dadmin.username, password="toto")
         response = self.client.get(url)
         self.assertEqual(response.status_code, 200)
-        self.assertIn("Latest news", response.content.decode('utf-8'))
+        self.assertIn("Latest news", response.content.decode("utf-8"))
         self.client.logout()
         self.client.login(username=self.user.username, password="toto")
         response = self.client.get(url)
diff --git a/modoboa/core/views/admin.py b/modoboa/core/views/admin.py
index 6771dedb1..3be4ef1d7 100644
--- a/modoboa/core/views/admin.py
+++ b/modoboa/core/views/admin.py
@@ -22,7 +22,7 @@ from .. import signals
 
 @login_required
 @user_passes_test(lambda u: u.is_superuser)
-def viewsettings(request, tplname='core/settings_header.html'):
+def viewsettings(request, tplname="core/settings_header.html"):
     return render(request, tplname, {
         "selection": "settings"
     })
@@ -71,7 +71,7 @@ def get_logs_page(request, page_id=None):
     """Return a page of logs."""
     sort_order, sort_dir = get_sort_order(
         request.GET, "date_created",
-        allowed_values=['date_created', 'level', 'logger', 'message']
+        allowed_values=["date_created", "level", "logger", "message"]
     )
     if page_id is None:
         page_id = request.GET.get("page", None)
diff --git a/modoboa/core/views/auth.py b/modoboa/core/views/auth.py
index 577263144..336d0d5bf 100644
--- a/modoboa/core/views/auth.py
+++ b/modoboa/core/views/auth.py
@@ -29,7 +29,7 @@ def dologin(request):
     if request.method == "POST":
         form = forms.LoginForm(request.POST)
         if form.is_valid():
-            logger = logging.getLogger('modoboa.auth')
+            logger = logging.getLogger("modoboa.auth")
             user = authenticate(username=form.cleaned_data["username"],
                                 password=form.cleaned_data["password"])
             if user and user.is_active:
diff --git a/modoboa/core/views/user.py b/modoboa/core/views/user.py
index 91acaff35..cafe1aeb2 100644
--- a/modoboa/core/views/user.py
+++ b/modoboa/core/views/user.py
@@ -27,7 +27,7 @@ def index(request, tplname="core/user_index.html"):
 
 
 @login_required
-def profile(request, tplname='core/user_profile.html'):
+def profile(request, tplname="core/user_profile.html"):
     """Profile detail/update view."""
     update_password = True
     results = signals.allow_password_change.send(
@@ -50,7 +50,7 @@ def profile(request, tplname='core/user_profile.html'):
                 request.user.language)
             return render_to_json_response(_("Profile updated"))
         return render_to_json_response(
-            {'form_errors': form.errors}, status=400)
+            {"form_errors": form.errors}, status=400)
 
     form = ProfileForm(update_password, instance=request.user)
     return render_to_json_response({
diff --git a/modoboa/lib/authbackends.py b/modoboa/lib/authbackends.py
index 18171afbb..0ff7fb645 100644
--- a/modoboa/lib/authbackends.py
+++ b/modoboa/lib/authbackends.py
@@ -86,7 +86,7 @@ try:
                 if grp.strip() in ldap_user.group_names:
                     group = "DomainAdmins"
                     break
-            if group == 'SimpleUsers':
+            if group == "SimpleUsers":
                 lpart, domain = split_mailbox(username)
                 if domain is None:
                     return None
diff --git a/modoboa/lib/cryptutils.py b/modoboa/lib/cryptutils.py
index 5f729bf50..25bc3ac9f 100644
--- a/modoboa/lib/cryptutils.py
+++ b/modoboa/lib/cryptutils.py
@@ -15,7 +15,7 @@ from cryptography.fernet import Fernet
 
 def random_key(length=16):
     """Generate a new key used to encrypt user passwords in session storage."""
-    chars = 'abcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*(-_=+)'
+    chars = "abcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*(-_=+)"
     return get_random_string(length, chars)
 
 
diff --git a/modoboa/lib/db_utils.py b/modoboa/lib/db_utils.py
index 8f6999aad..31f642e71 100644
--- a/modoboa/lib/db_utils.py
+++ b/modoboa/lib/db_utils.py
@@ -25,7 +25,7 @@ def db_type(cname="default"):
     if cname not in settings.DATABASES:
         raise InternalError(
             _("Connection to database %s not configured" % cname))
-    for t in ['postgres', 'mysql', 'sqlite']:
-        if settings.DATABASES[cname]['ENGINE'].find(t) != -1:
+    for t in ["postgres", "mysql", "sqlite"]:
+        if settings.DATABASES[cname]["ENGINE"].find(t) != -1:
             return t
     return None
diff --git a/modoboa/lib/email_utils.py b/modoboa/lib/email_utils.py
index f043c039c..ae12a13c7 100644
--- a/modoboa/lib/email_utils.py
+++ b/modoboa/lib/email_utils.py
@@ -128,7 +128,7 @@ class Email(object):
         # msg parameter to maintain compatibility with
         # modoboa_webmail.lib.imapemail.ImapEmail
         if header in msg:
-            return "".join([smart_text(v, encoding=(e or 'ascii'))
+            return "".join([smart_text(v, encoding=(e or "ascii"))
                             for v, e in email.header.decode_header(msg[header])
                             ])
         return ""
@@ -188,7 +188,7 @@ class Email(object):
         cid = None
         if "Content-ID" in msg:
             cid = msg["Content-ID"]
-            if cid.startswith('<') and cid.endswith('>'):
+            if cid.startswith("<") and cid.endswith(">"):
                 cid = cid[1:-1]
         else:
             matches = _RE_CID.match(msg["Content-Type"])
@@ -379,7 +379,7 @@ def set_email_headers(msg, subject, sender, rcpt):
     """
     import pkg_resources
 
-    msg["Subject"] = Header(subject, 'utf8')
+    msg["Subject"] = Header(subject, "utf8")
     msg["From"] = sender
     msg["To"] = prepare_addresses(rcpt)
     msg["Message-ID"] = make_msgid()
@@ -388,7 +388,7 @@ def set_email_headers(msg, subject, sender, rcpt):
     msg["Date"] = formatdate(time.time(), True)
 
 
-def __sendmail(sender, rcpt, msgstring, server='localhost', port=25):
+def __sendmail(sender, rcpt, msgstring, server="localhost", port=25):
     """Message sending
 
     Return a tuple (True, None) on success, (False, error message)
@@ -425,7 +425,7 @@ def sendmail_simple(
     :param content: message's content
     :return: tuple
     """
-    msg = MIMEText(content, _charset='utf-8')
+    msg = MIMEText(content, _charset="utf-8")
     set_email_headers(msg, subject, sender, rcpt)
     return __sendmail(sender, rcpt, msg.as_string(), **kwargs)
 
diff --git a/modoboa/lib/exceptions.py b/modoboa/lib/exceptions.py
index 4bdd15896..3bfb5915f 100644
--- a/modoboa/lib/exceptions.py
+++ b/modoboa/lib/exceptions.py
@@ -17,9 +17,9 @@ class ModoboaException(Exception):
     http_code = None
 
     def __init__(self, *args, **kwargs):
-        if 'http_code' in kwargs:
-            self.http_code = kwargs['http_code']
-            del kwargs['http_code']
+        if "http_code" in kwargs:
+            self.http_code = kwargs["http_code"]
+            del kwargs["http_code"]
         super(ModoboaException, self).__init__(*args, **kwargs)
 
 
diff --git a/modoboa/lib/form_utils.py b/modoboa/lib/form_utils.py
index 74abb7a37..2b5bcdf95 100644
--- a/modoboa/lib/form_utils.py
+++ b/modoboa/lib/form_utils.py
@@ -19,7 +19,7 @@ from modoboa.lib.exceptions import BadRequest
 from modoboa.lib.web_utils import render_to_json_response
 
 
-ABC = abc.ABCMeta(force_str('ABC'), (object,), {})
+ABC = abc.ABCMeta(force_str("ABC"), (object,), {})
 
 
 class WizardStep(object):
@@ -87,7 +87,7 @@ class WizardForm(ABC):
         result = {}
         for step in self.steps:
             for name, value in list(step.form.errors.items()):
-                if name == '__all__':
+                if name == "__all__":
                     continue
                 result[name] = value
         return result
@@ -283,8 +283,8 @@ class TabForms(object):
         """
         result = {}
         for f in self.forms:
-            for name, value in list(f['instance'].errors.items()):
-                if name == '__all__':
+            for name, value in list(f["instance"].errors.items()):
+                if name == "__all__":
                     continue
                 result[name] = value
         return result
@@ -298,9 +298,9 @@ class TabForms(object):
         to_remove = []
         for f in self.forms:
             if mandatory_only and \
-               ('mandatory' not in f or not f["mandatory"]):
+               ("mandatory" not in f or not f["mandatory"]):
                 continue
-            elif optional_only and ('mandatory' in f and f["mandatory"]):
+            elif optional_only and ("mandatory" in f and f["mandatory"]):
                 continue
             if not self._before_is_valid(f):
                 to_remove.append(f)
@@ -349,7 +349,7 @@ class TabForms(object):
                 self.save()
                 return self.done()
             return render_to_json_response(
-                {'form_errors': self.errors}, status=400
+                {"form_errors": self.errors}, status=400
             )
         context = {
             "tabs": self,
diff --git a/modoboa/lib/imap_utf7.py b/modoboa/lib/imap_utf7.py
index f1a2af3bd..050e92a35 100644
--- a/modoboa/lib/imap_utf7.py
+++ b/modoboa/lib/imap_utf7.py
@@ -61,13 +61,13 @@ PRINTABLE = set(range(0x20, 0x26)) | set(range(0x27, 0x7f))
 
 
 def modified_utf7(s):
-    s_utf7 = s.encode('utf-7')
-    return s_utf7[1:-1].replace(b'/', b',')
+    s_utf7 = s.encode("utf-7")
+    return s_utf7[1:-1].replace(b"/", b",")
 
 
 def doB64(_in, r):
     if _in:
-        r.extend([b'&', modified_utf7(''.join(_in)), b'-'])
+        r.extend([b"&", modified_utf7("".join(_in)), b"-"])
         del _in[:]
 
 
@@ -78,32 +78,32 @@ def encoder(s):
         if ord(c) in PRINTABLE:
             doB64(_in, r)
             r.append(c.encode())
-        elif c == '&':
+        elif c == "&":
             doB64(_in, r)
-            r.append(b'&-')
+            r.append(b"&-")
         else:
             _in.append(c)
     doB64(_in, r)
-    return (b''.join(r), len(s))
+    return (b"".join(r), len(s))
 
 
 # decoding
 
 
 def modified_unutf7(s):
-    s_utf7 = b'+' + s.replace(b',', b'/') + b'-'
-    return s_utf7.decode('utf-7')
+    s_utf7 = b"+" + s.replace(b",", b"/") + b"-"
+    return s_utf7.decode("utf-7")
 
 
 def decoder(s):
     r = []
     decoded = bytearray()
     for c in s:
-        if c == ord('&') and not decoded:
-            decoded.append(ord('&'))
-        elif c == ord('-') and decoded:
+        if c == ord("&") and not decoded:
+            decoded.append(ord("&"))
+        elif c == ord("-") and decoded:
             if len(decoded) == 1:
-                r.append('&')
+                r.append("&")
             else:
                 r.append(modified_unutf7(decoded[1:]))
             decoded = bytearray()
@@ -113,22 +113,22 @@ def decoder(s):
             r.append(chr(c))
     if decoded:
         r.append(modified_unutf7(decoded[1:]))
-    bin_str = ''.join(r)
+    bin_str = "".join(r)
     return (bin_str, len(s))
 
 
 class StreamReader(codecs.StreamReader):
-    def decode(self, s, errors='strict'):
+    def decode(self, s, errors="strict"):
         return decoder(s)
 
 
 class StreamWriter(codecs.StreamWriter):
-    def decode(self, s, errors='strict'):
+    def decode(self, s, errors="strict"):
         return encoder(s)
 
 
 def imap4_utf_7(name):
-    if name == 'imap4-utf-7':
+    if name == "imap4-utf-7":
         return (encoder, decoder, StreamReader, StreamWriter)
 
 
@@ -139,7 +139,7 @@ codecs.register(imap4_utf_7)
 
 def imapUTF7Encode(ust):
     "Returns imap utf-7 encoded version of string"
-    return ust.encode('imap4-utf-7')
+    return ust.encode("imap4-utf-7")
 
 
 def imapUTF7EncodeSequence(seq):
@@ -149,7 +149,7 @@ def imapUTF7EncodeSequence(seq):
 
 def imapUTF7Decode(st):
     "Returns utf7 encoded version of imap utf-7 string"
-    return st.decode('imap4-utf-7')
+    return st.decode("imap4-utf-7")
 
 
 def imapUTF7DecodeSequence(seq):
@@ -159,17 +159,17 @@ def imapUTF7DecodeSequence(seq):
 
 def utf8Decode(st):
     "Returns utf7 encoded version of imap utf-7 string"
-    return st.decode('utf-8')
+    return st.decode("utf-8")
 
 
 def utf7SequenceToUTF8(seq):
     "Returns utf7 encoded version of imap utf-7 strings in sequence"
-    return [itm.decode('imap4-utf-7').encode('utf-8') for itm in seq]
+    return [itm.decode("imap4-utf-7").encode("utf-8") for itm in seq]
 
 
-__all__ = ['imapUTF7Encode', 'imapUTF7Decode', ]
+__all__ = ["imapUTF7Encode", "imapUTF7Decode", ]
 
-if __name__ == '__main__':
+if __name__ == "__main__":
 
     # print u'bøx'.encode('imap4-utf-7')
     # print 'expected b&APg-x'
@@ -177,29 +177,29 @@ if __name__ == '__main__':
     # print u'båx'.encode('imap4-utf-7')
     # print 'expected b&AOU-x'
 
-    print('#######')
-    print('bøx')
+    print("#######")
+    print("bøx")
     e = imapUTF7Encode(u'bøx')
     print(e)
-    print(imapUTF7Decode(e).encode('latin-1'))
+    print(imapUTF7Decode(e).encode("latin-1"))
 
-    print('#######')
-    print('båx')
+    print("#######")
+    print("båx")
     e = imapUTF7Encode(u'båx')
     print(e)
-    print(imapUTF7Decode(e).encode('latin-1'))
+    print(imapUTF7Decode(e).encode("latin-1"))
 
-    print('#######')
-    print('~/bågø')
+    print("#######")
+    print("~/bågø")
     e = imapUTF7Encode(u'~/bågø')
     print(e)
-    print(imapUTF7Decode(e).encode('latin-1'))
+    print(imapUTF7Decode(e).encode("latin-1"))
 
-    print('#######')
-    print('Ting & Såger')
+    print("#######")
+    print("Ting & Såger")
     e = imapUTF7Encode(u'Ting & Såger')
     print(e)
-    print(imapUTF7Decode(e).encode('latin-1'))
+    print(imapUTF7Decode(e).encode("latin-1"))
 
     # e = imapUTF7Decode('b&AOU-x')
     # print e.encode('latin-1')
@@ -207,13 +207,13 @@ if __name__ == '__main__':
     # e = imapUTF7Decode('b&APg-x')
     # print e.encode('latin-1')
 
-    print('#######')
-    print('~/Følder/mailbåx & stuff + more')
+    print("#######")
+    print("~/Følder/mailbåx & stuff + more")
     n = u'~/Følder/mailbåx & stuff + more'
     e = imapUTF7Encode(n)
     print(e)
-    print(imapUTF7Decode(e).encode('latin-1'))
+    print(imapUTF7Decode(e).encode("latin-1"))
 
-    print('#######')
-    print('~peter/mail/&ZeVnLIqe-/&U,BTFw-')
-    print(imapUTF7Decode('~peter/mail/&ZeVnLIqe-/&U,BTFw-').encode('utf-8'))
+    print("#######")
+    print("~peter/mail/&ZeVnLIqe-/&U,BTFw-")
+    print(imapUTF7Decode("~peter/mail/&ZeVnLIqe-/&U,BTFw-").encode("utf-8"))
diff --git a/modoboa/lib/ldap_utils.py b/modoboa/lib/ldap_utils.py
index 57767b69f..d031bd41f 100644
--- a/modoboa/lib/ldap_utils.py
+++ b/modoboa/lib/ldap_utils.py
@@ -72,7 +72,7 @@ class LDAPAuthBackend(object):
         """Get a connection from the server."""
         kwargs = {}
         if six.PY3:
-            kwargs['bytes_mode'] = False
+            kwargs["bytes_mode"] = False
         conn = ldap.initialize(self.server_uri, **kwargs)
         conn.set_option(ldap.OPT_X_TLS_DEMAND, True)
         conn.set_option(ldap.OPT_DEBUG_LEVEL, 255)
@@ -121,7 +121,7 @@ class LDAPAuthBackend(object):
         user_dn = self._find_user_dn(user)
         if self.ldap_ad:
             newpassword = (
-                ('"%s"' % newpassword).encode('utf-16').lstrip('\377\376')
+                ('"%s"' % newpassword).encode("utf-16").lstrip("\377\376")
             )
         ldif = [(ldap.MOD_REPLACE,
                  self.pwd_attr,
diff --git a/modoboa/lib/singleton.py b/modoboa/lib/singleton.py
index da4210794..f4444be7f 100644
--- a/modoboa/lib/singleton.py
+++ b/modoboa/lib/singleton.py
@@ -11,5 +11,5 @@ class _Singleton(type):
         return cls._instances[cls]
 
 
-class Singleton(_Singleton('SingletonMeta', (object,), {})):
+class Singleton(_Singleton("SingletonMeta", (object,), {})):
     pass
diff --git a/modoboa/lib/templatetags/lib_tags.py b/modoboa/lib/templatetags/lib_tags.py
index ef7a9da2d..e1abb842f 100644
--- a/modoboa/lib/templatetags/lib_tags.py
+++ b/modoboa/lib/templatetags/lib_tags.py
@@ -16,7 +16,7 @@ register = template.Library()
 
 
 @register.simple_tag
-def join(items, sep=','):
+def join(items, sep=","):
     res = ""
     for k, v in list(items.items()):
         if res != "":
@@ -100,7 +100,7 @@ def extra_static_content(caller, st_type, user):
     )
 
 
-@register.filter(name='localize_header_name')
+@register.filter(name="localize_header_name")
 def localize_header_name(headername):
     """ Localizes the header names """
     names = {
diff --git a/modoboa/lib/tests/__init__.py b/modoboa/lib/tests/__init__.py
index ace3d977e..86b2e9ece 100644
--- a/modoboa/lib/tests/__init__.py
+++ b/modoboa/lib/tests/__init__.py
@@ -17,7 +17,7 @@ from modoboa.core import models as core_models
 from .. import sysutils
 
 try:
-    s = socket.create_connection(('127.0.0.1', 25))
+    s = socket.create_connection(("127.0.0.1", 25))
     s.close()
     NO_SMTP = False
 except socket.error:
@@ -72,21 +72,21 @@ class ModoTestCase(ParametersMixin, TestCase):
         if params is None:
             params = {}
         response = getattr(self.client, method)(
-            url, params, HTTP_X_REQUESTED_WITH='XMLHttpRequest')
+            url, params, HTTP_X_REQUESTED_WITH="XMLHttpRequest")
         self.assertEqual(response.status_code, status)
         return response.json()
 
     def ajax_post(self, *args, **kwargs):
-        return self.ajax_request('post', *args, **kwargs)
+        return self.ajax_request("post", *args, **kwargs)
 
     def ajax_put(self, *args, **kwargs):
-        return self.ajax_request('put', *args, **kwargs)
+        return self.ajax_request("put", *args, **kwargs)
 
     def ajax_delete(self, *args, **kwargs):
-        return self.ajax_request('delete', *args, **kwargs)
+        return self.ajax_request("delete", *args, **kwargs)
 
     def ajax_get(self, *args, **kwargs):
-        return self.ajax_request('get', *args, **kwargs)
+        return self.ajax_request("get", *args, **kwargs)
 
 
 class ModoAPITestCase(ParametersMixin, APITestCase):
@@ -103,4 +103,4 @@ class ModoAPITestCase(ParametersMixin, APITestCase):
     def setUp(self):
         """Setup."""
         super(ModoAPITestCase, self).setUp()
-        self.client.credentials(HTTP_AUTHORIZATION='Token ' + self.token.key)
+        self.client.credentials(HTTP_AUTHORIZATION="Token " + self.token.key)
diff --git a/modoboa/lib/tests/test_u2u_decode.py b/modoboa/lib/tests/test_u2u_decode.py
index b06bf38c6..9c64cae46 100644
--- a/modoboa/lib/tests/test_u2u_decode.py
+++ b/modoboa/lib/tests/test_u2u_decode.py
@@ -49,12 +49,12 @@ class U2UTestCase(TestCase):
         )
         mailsploit_sample = (
             '"=?utf-8?b?cG90dXNAd2hpdGVob3VzZS5nb3Y=?==?utf-8?Q?=0A=00?="\n'
-            '<=?utf-8?b?cG90dXNAd2hpdGVob3VzZS5nb3Y=?==?utf-8?Q?=0A=00?='
-            '@mailsploit.com>')
+            "<=?utf-8?b?cG90dXNAd2hpdGVob3VzZS5nb3Y=?==?utf-8?Q?=0A=00?="
+            "@mailsploit.com>")
         expected_result = (
-            'potus@whitehouse.gov',
-            '=?utf-8?b?cG90dXNAd2hpdGVob3VzZS5nb3Y=?==?utf-8?Q??='
-            '@mailsploit.com')
+            "potus@whitehouse.gov",
+            "=?utf-8?b?cG90dXNAd2hpdGVob3VzZS5nb3Y=?==?utf-8?Q??="
+            "@mailsploit.com")
         self.assertEqual(
             u2u_decode.decode_address(mailsploit_sample),
             expected_result)
diff --git a/modoboa/lib/web_utils.py b/modoboa/lib/web_utils.py
index 2596c94de..8870e86ad 100644
--- a/modoboa/lib/web_utils.py
+++ b/modoboa/lib/web_utils.py
@@ -88,7 +88,7 @@ def render_to_json_response(context, **response_kwargs):
     :return: ``HttpResponse`` object
     """
     data = json.dumps(context)
-    response_kwargs['content_type'] = 'application/json'
+    response_kwargs["content_type"] = "application/json"
     return HttpResponse(data, **response_kwargs)
 
 
@@ -136,8 +136,8 @@ class NavigationParameters(object):
     def __init__(self, request, sessionkey):
         self.request = request
         self.sessionkey = sessionkey
-        self.parameters = [('pattern', '', True),
-                           ('criteria', 'from_addr', False)]
+        self.parameters = [("pattern", "", True),
+                           ("criteria", "from_addr", False)]
 
     def __getitem__(self, key):
         """Retrieve an item."""
diff --git a/modoboa/limits/tests/test_api.py b/modoboa/limits/tests/test_api.py
index 4707c244b..0b2194897 100644
--- a/modoboa/limits/tests/test_api.py
+++ b/modoboa/limits/tests/test_api.py
@@ -41,7 +41,7 @@ class APIAdminLimitsTestCase(lib_tests.ModoAPITestCase):
     def test_domadmins_limit(self):
         """Check domain admins limit."""
         self.client.credentials(
-            HTTP_AUTHORIZATION='Token ' + self.r_token.key)
+            HTTP_AUTHORIZATION="Token " + self.r_token.key)
 
         limit = self.reseller.userobjectlimit_set.get(name="domain_admins")
         url = reverse("api:account-list")
@@ -82,7 +82,7 @@ class APIAdminLimitsTestCase(lib_tests.ModoAPITestCase):
     def test_domains_limit(self):
         """Check domains limit."""
         self.client.credentials(
-            HTTP_AUTHORIZATION='Token ' + self.r_token.key)
+            HTTP_AUTHORIZATION="Token " + self.r_token.key)
         limit = self.reseller.userobjectlimit_set.get(name="domains")
         quota = self.reseller.userobjectlimit_set.get(name="quota")
         quota.max_value = 3
@@ -104,7 +104,7 @@ class APIAdminLimitsTestCase(lib_tests.ModoAPITestCase):
         response = self.client.post(url, data, format="json")
         self.assertEqual(response.status_code, 403)
         self.assertEqual(
-            response.content.decode('utf-8'), '"Domains: limit reached"'
+            response.content.decode("utf-8"), '"Domains: limit reached"'
         )
 
         self.client.delete(
@@ -120,7 +120,7 @@ class APIAdminLimitsTestCase(lib_tests.ModoAPITestCase):
     def test_domain_aliases_limit(self):
         """Check domain aliases limit."""
         self.client.credentials(
-            HTTP_AUTHORIZATION='Token ' + self.r_token.key)
+            HTTP_AUTHORIZATION="Token " + self.r_token.key)
         domain = Domain.objects.get(name="test.com")
         domain.add_admin(self.reseller)
         limit = self.reseller.userobjectlimit_set.get(name="domain_aliases")
@@ -142,7 +142,7 @@ class APIAdminLimitsTestCase(lib_tests.ModoAPITestCase):
     def test_mailboxes_limit(self):
         """Check mailboxes limit."""
         self.client.credentials(
-            HTTP_AUTHORIZATION='Token ' + self.da_token.key)
+            HTTP_AUTHORIZATION="Token " + self.da_token.key)
 
         limit = self.user.userobjectlimit_set.get(name="mailboxes")
         url = reverse("api:account-list")
@@ -173,7 +173,7 @@ class APIAdminLimitsTestCase(lib_tests.ModoAPITestCase):
     def test_aliases_limit(self):
         """Check mailbox aliases limit."""
         self.client.credentials(
-            HTTP_AUTHORIZATION='Token ' + self.da_token.key)
+            HTTP_AUTHORIZATION="Token " + self.da_token.key)
 
         limit = self.user.userobjectlimit_set.get(name="mailbox_aliases")
         url = reverse("api:alias-list")
diff --git a/modoboa/limits/tests/test_user_limits.py b/modoboa/limits/tests/test_user_limits.py
index 39168a24b..f5387bcf3 100644
--- a/modoboa/limits/tests/test_user_limits.py
+++ b/modoboa/limits/tests/test_user_limits.py
@@ -30,7 +30,7 @@ class PermissionsTestCase(lib_tests.ModoTestCase):
         values = dict(
             username="reseller@test.com", first_name="Reseller", last_name="",
             password1="Toto1234", password2="Toto1234", role="Resellers",
-            is_active=True, email="reseller@test.com", stepid='step2'
+            is_active=True, email="reseller@test.com", stepid="step2"
         )
         self.ajax_post(reverse("admin:account_add"), values)
         account = User.objects.get(username="reseller@test.com")
@@ -60,19 +60,19 @@ class ResourceTestCase(lib_tests.ModoTestCase):
         populate_database()
 
     def _create_account(
-            self, username, role='SimpleUsers', status=200, **kwargs):
+            self, username, role="SimpleUsers", status=200, **kwargs):
         values = dict(
             username=username, first_name="Tester", last_name="Toto",
             password1="Toto1234", password2="Toto1234", role=role,
             quota_act=True,
-            is_active=True, email=username, stepid='step2',
+            is_active=True, email=username, stepid="step2",
         )
         values.update(kwargs)
         return self.ajax_post(
             reverse("admin:account_add"), values, status
         )
 
-    def _create_alias(self, email, rcpt='user@test.com', status=200):
+    def _create_alias(self, email, rcpt="user@test.com", status=200):
         values = dict(
             address=email, recipients=rcpt, enabled=True
         )
@@ -130,7 +130,7 @@ class DomainAdminTestCase(ResourceTestCase):
     def setUpTestData(cls):
         """Create test data."""
         super(DomainAdminTestCase, cls).setUpTestData()
-        cls.user = User.objects.get(username='admin@test.com')
+        cls.user = User.objects.get(username="admin@test.com")
         cls.user.userobjectlimit_set.filter(
             name__in=["mailboxes", "mailbox_aliases"]).update(max_value=2)
 
@@ -140,40 +140,40 @@ class DomainAdminTestCase(ResourceTestCase):
         self.client.force_login(self.user)
 
     def test_mailboxes_limit(self):
-        self._create_account('tester1@test.com')
-        self._check_limit('mailboxes', 1, 2)
-        self._create_account('tester2@test.com')
-        self._check_limit('mailboxes', 2, 2)
-        self._create_account('tester3@test.com', status=403)
-        self._check_limit('mailboxes', 2, 2)
+        self._create_account("tester1@test.com")
+        self._check_limit("mailboxes", 1, 2)
+        self._create_account("tester2@test.com")
+        self._check_limit("mailboxes", 2, 2)
+        self._create_account("tester3@test.com", status=403)
+        self._check_limit("mailboxes", 2, 2)
         self.ajax_post(
-            reverse('admin:account_delete',
-                    args=[User.objects.get(username='tester2@test.com').id]),
+            reverse("admin:account_delete",
+                    args=[User.objects.get(username="tester2@test.com").id]),
             {}
         )
-        self._check_limit('mailboxes', 1, 2)
+        self._check_limit("mailboxes", 1, 2)
 
     def test_aliases_limit(self):
-        self._create_alias('alias1@test.com')
-        self._check_limit('mailbox_aliases', 1, 2)
-        self._create_alias('alias2@test.com')
-        self._check_limit('mailbox_aliases', 2, 2)
-        self._create_alias('alias3@test.com', status=403)
-        self._check_limit('mailbox_aliases', 2, 2)
+        self._create_alias("alias1@test.com")
+        self._check_limit("mailbox_aliases", 1, 2)
+        self._create_alias("alias2@test.com")
+        self._check_limit("mailbox_aliases", 2, 2)
+        self._create_alias("alias3@test.com", status=403)
+        self._check_limit("mailbox_aliases", 2, 2)
         # Set unlimited value
         self.user.userobjectlimit_set.filter(name="mailbox_aliases").update(
             max_value=-1)
-        self._create_alias('alias3@test.com')
-        self._check_limit('mailbox_aliases', 3, -1)
+        self._create_alias("alias3@test.com")
+        self._check_limit("mailbox_aliases", 3, -1)
         self.ajax_post(
-            reverse('admin:alias_delete') + '?selection=%d'
-            % Alias.objects.get(address='alias2@test.com').id,
+            reverse("admin:alias_delete") + "?selection=%d"
+            % Alias.objects.get(address="alias2@test.com").id,
             {}
         )
-        self._check_limit('mailbox_aliases', 2, -1)
+        self._check_limit("mailbox_aliases", 2, -1)
 
     def test_aliases_limit_through_account_form(self):
-        user = User.objects.get(username='user@test.com')
+        user = User.objects.get(username="user@test.com")
         values = dict(
             username=user.username, role=user.role,
             is_active=user.is_active, email=user.email, quota_act=True,
@@ -184,8 +184,8 @@ class DomainAdminTestCase(ResourceTestCase):
             reverse("admin:account_change", args=[user.id]),
             values
         )
-        Alias.objects.get(address='alias1@test.com')
-        self._check_limit('mailbox_aliases', 2, 2)
+        Alias.objects.get(address="alias1@test.com")
+        self._check_limit("mailbox_aliases", 2, 2)
 
 
 class ResellerTestCase(ResourceTestCase):
@@ -197,7 +197,7 @@ class ResellerTestCase(ResourceTestCase):
         cls.localconfig.parameters.set_value("deflt_user_quota_limit", 1000)
         cls.localconfig.save()
         cls.user = UserFactory(
-            username='reseller', groups=('Resellers',)
+            username="reseller", groups=("Resellers",)
         )
 
     def setUp(self):
@@ -209,32 +209,32 @@ class ResellerTestCase(ResourceTestCase):
         response = self.client.get(reverse("admin:domain_list"))
         self.assertContains(response, "Domains (0%)")
         self.assertContains(response, "Domain aliases (0%)")
-        self._create_domain('domain1.tld')
-        self._check_limit('domains', 1, 2)
-        self._create_domain('domain2.tld')
-        self._check_limit('domains', 2, 2)
-        self._create_domain('domain3.tld', 403)
-        self._check_limit('domains', 2, 2)
+        self._create_domain("domain1.tld")
+        self._check_limit("domains", 1, 2)
+        self._create_domain("domain2.tld")
+        self._check_limit("domains", 2, 2)
+        self._create_domain("domain3.tld", 403)
+        self._check_limit("domains", 2, 2)
         self.ajax_post(
-            reverse('admin:domain_delete',
-                    args=[Domain.objects.get(name='domain2.tld').id]),
+            reverse("admin:domain_delete",
+                    args=[Domain.objects.get(name="domain2.tld").id]),
             {}
         )
-        self._check_limit('domains', 1, 2)
+        self._check_limit("domains", 1, 2)
 
     def test_domain_aliases_limit(self):
-        self._create_domain('pouet.com')
-        self._domain_alias_operation('add', 'pouet.com', 'domain-alias1.tld')
-        self._check_limit('domain_aliases', 1, 2)
-        self._domain_alias_operation('add', 'pouet.com', 'domain-alias2.tld')
-        self._check_limit('domain_aliases', 2, 2)
+        self._create_domain("pouet.com")
+        self._domain_alias_operation("add", "pouet.com", "domain-alias1.tld")
+        self._check_limit("domain_aliases", 1, 2)
+        self._domain_alias_operation("add", "pouet.com", "domain-alias2.tld")
+        self._check_limit("domain_aliases", 2, 2)
         self._domain_alias_operation(
-            'add', 'pouet.com', 'domain-alias3.tld', 403
+            "add", "pouet.com", "domain-alias3.tld", 403
         )
-        self._check_limit('domain_aliases', 2, 2)
+        self._check_limit("domain_aliases", 2, 2)
         self._domain_alias_operation(
-            'delete', 'pouet.com', 'domain-alias2.tld')
-        self._check_limit('domain_aliases', 1, 2)
+            "delete", "pouet.com", "domain-alias2.tld")
+        self._check_limit("domain_aliases", 1, 2)
 
     def test_domain_admins_limit(self):
         response = self.client.get(reverse("admin:identity_list"))
@@ -242,21 +242,21 @@ class ResellerTestCase(ResourceTestCase):
         self.assertContains(response, "Mailboxes (0%)")
         self.assertContains(response, "Mailbox aliases (0%)")
 
-        self._create_domain('domain.tld')
-        self._create_account('admin1@domain.tld', role='DomainAdmins')
-        self._check_limit('domain_admins', 1, 2)
-        self._create_account('admin2@domain.tld', role='DomainAdmins')
-        self._check_limit('domain_admins', 2, 2)
+        self._create_domain("domain.tld")
+        self._create_account("admin1@domain.tld", role="DomainAdmins")
+        self._check_limit("domain_admins", 1, 2)
+        self._create_account("admin2@domain.tld", role="DomainAdmins")
+        self._check_limit("domain_admins", 2, 2)
         resp = self._create_account(
-            'admin3@domain.tld',
-            role='DomainAdmins',
+            "admin3@domain.tld",
+            role="DomainAdmins",
             status=400)
         self.assertEqual(
-            resp['form_errors']['role'][0],
-            'Select a valid choice. DomainAdmins is not one of the available '
-            'choices.'
+            resp["form_errors"]["role"][0],
+            "Select a valid choice. DomainAdmins is not one of the available "
+            "choices."
         )
-        self._check_limit('domain_admins', 2, 2)
+        self._check_limit("domain_admins", 2, 2)
 
         self.user.userobjectlimit_set.filter(
             name="mailboxes").update(max_value=3)
@@ -272,17 +272,17 @@ class ResellerTestCase(ResourceTestCase):
             values, status=400
         )
         self.assertEqual(
-            resp['form_errors']['role'][0],
-            'Select a valid choice. DomainAdmins is not one of the available '
-            'choices.'
+            resp["form_errors"]["role"][0],
+            "Select a valid choice. DomainAdmins is not one of the available "
+            "choices."
         )
-        self._check_limit('domain_admins', 2, 2)
+        self._check_limit("domain_admins", 2, 2)
 
     def test_domain_admin_resource_are_empty(self):
-        self._create_domain('domain.tld')
-        self._create_account('admin1@domain.tld', role='DomainAdmins')
-        domadmin = User.objects.get(username='admin1@domain.tld')
-        for l in ['mailboxes', 'mailbox_aliases']:
+        self._create_domain("domain.tld")
+        self._create_account("admin1@domain.tld", role="DomainAdmins")
+        domadmin = User.objects.get(username="admin1@domain.tld")
+        for l in ["mailboxes", "mailbox_aliases"]:
             self.assertEqual(
                 domadmin.userobjectlimit_set.get(name=l).max_value, 0
             )
@@ -290,13 +290,13 @@ class ResellerTestCase(ResourceTestCase):
     def test_domain_admins_limit_from_domain_tpl(self):
         self.user.userobjectlimit_set.filter(
             name="domains").update(max_value=3)
-        self._create_domain('domain1.tld', withtpl=True)
-        self._create_domain('domain2.tld', withtpl=True)
-        self._check_limit('domain_admins', 2, 2)
-        self._check_limit('domains', 2, 3)
-        self._create_domain('domain3.tld', status=200, withtpl=True)
-        self._check_limit('domain_admins', 2, 2)
-        self._check_limit('domains', 3, 3)
+        self._create_domain("domain1.tld", withtpl=True)
+        self._create_domain("domain2.tld", withtpl=True)
+        self._check_limit("domain_admins", 2, 2)
+        self._check_limit("domains", 2, 3)
+        self._create_domain("domain3.tld", status=200, withtpl=True)
+        self._check_limit("domain_admins", 2, 2)
+        self._check_limit("domains", 3, 3)
 
     def test_quota(self):
         """Check quota resource."""
@@ -353,51 +353,51 @@ class ResellerTestCase(ResourceTestCase):
 
     def test_reseller_deletes_domain(self):
         """Check if all resources are restored after the deletion."""
-        self._create_domain('domain.tld', withtpl=True)
+        self._create_domain("domain.tld", withtpl=True)
         dom = Domain.objects.get(name="domain.tld")
         self.ajax_post(
             reverse("admin:domain_delete", args=[dom.id]),
             {}
         )
-        self._check_limit('domains', 0, 2)
-        self._check_limit('domain_admins', 1, 2)
-        self._check_limit('mailboxes', 0, 2)
-        self._check_limit('mailbox_aliases', 0, 2)
+        self._check_limit("domains", 0, 2)
+        self._check_limit("domain_admins", 1, 2)
+        self._check_limit("mailboxes", 0, 2)
+        self._check_limit("mailbox_aliases", 0, 2)
 
     def test_sadmin_removes_ownership(self):
-        self._create_domain('domain.tld', withtpl=True)
+        self._create_domain("domain.tld", withtpl=True)
         dom = Domain.objects.get(name="domain.tld")
         self.client.logout()
-        self.client.login(username='admin', password='password')
+        self.client.login(username="admin", password="password")
         self.ajax_get(
             "{0}?domid={1}&daid={2}".format(
-                reverse('admin:permission_remove'),
+                reverse("admin:permission_remove"),
                 dom.id, self.user.id
             ), {}
         )
-        self._check_limit('domains', 0, 2)
-        self._check_limit('domain_admins', 0, 2)
-        self._check_limit('mailboxes', 0, 2)
-        self._check_limit('mailbox_aliases', 0, 2)
+        self._check_limit("domains", 0, 2)
+        self._check_limit("domain_admins", 0, 2)
+        self._check_limit("mailboxes", 0, 2)
+        self._check_limit("mailbox_aliases", 0, 2)
 
     def test_allocate_from_pool(self):
-        self._create_domain('domain.tld')
-        self._create_account('admin1@domain.tld', role='DomainAdmins')
-        user = User.objects.get(username='admin1@domain.tld')
+        self._create_domain("domain.tld")
+        self._create_account("admin1@domain.tld", role="DomainAdmins")
+        user = User.objects.get(username="admin1@domain.tld")
 
         # Give 1 mailbox and 2 aliases to the admin -> should work
         values = {
-            'username': user.username, 'role': user.role, 'quota_act': True,
-            'is_active': user.is_active, 'email': user.email,
-            'mailboxes_limit': 1, 'mailbox_aliases_limit': 2,
-            'language': 'en'
+            "username": user.username, "role": user.role, "quota_act": True,
+            "is_active": user.is_active, "email": user.email,
+            "mailboxes_limit": 1, "mailbox_aliases_limit": 2,
+            "language": "en"
         }
         self.ajax_post(
             reverse("admin:account_change", args=[user.id]),
             values
         )
-        self._check_limit('mailboxes', 1, 1)
-        self._check_limit('mailbox_aliases', 0, 0)
+        self._check_limit("mailboxes", 1, 1)
+        self._check_limit("mailbox_aliases", 0, 0)
 
         # Delete the admin -> resources should go back to the
         # reseller's pool
@@ -405,20 +405,20 @@ class ResellerTestCase(ResourceTestCase):
             reverse("admin:account_delete", args=[user.id]),
             {}
         )
-        self._check_limit('mailboxes', 0, 2)
-        self._check_limit('mailbox_aliases', 0, 2)
+        self._check_limit("mailboxes", 0, 2)
+        self._check_limit("mailbox_aliases", 0, 2)
 
     def test_restore_resources(self):
         """Give resource to a domain admin and restore them."""
-        self._create_domain('domain.tld')
-        dom = Domain.objects.get(name='domain.tld')
-        self._create_account('admin1@domain.tld', role='DomainAdmins')
-        user = User.objects.get(username='admin1@domain.tld')
+        self._create_domain("domain.tld")
+        dom = Domain.objects.get(name="domain.tld")
+        self._create_account("admin1@domain.tld", role="DomainAdmins")
+        user = User.objects.get(username="admin1@domain.tld")
         values = {
-            'username': user.username, 'role': user.role, 'quota_act': True,
-            'is_active': user.is_active, 'email': user.email,
-            'mailboxes_limit': 1, 'mailbox_aliases_limit': 2,
-            'language': 'en'
+            "username": user.username, "role": user.role, "quota_act": True,
+            "is_active": user.is_active, "email": user.email,
+            "mailboxes_limit": 1, "mailbox_aliases_limit": 2,
+            "language": "en"
         }
         self.ajax_post(
             reverse("admin:account_change", args=[user.id]),
@@ -426,71 +426,71 @@ class ResellerTestCase(ResourceTestCase):
         )
         dom.add_admin(user)
         self.client.logout()
-        self.client.login(username='admin1@domain.tld', password='Toto1234')
-        self._create_account('user1@domain.tld')
-        self._create_alias('alias1@domain.tld', 'user1@domain.tld')
-        self._create_alias('alias2@domain.tld', 'user1@domain.tld')
+        self.client.login(username="admin1@domain.tld", password="Toto1234")
+        self._create_account("user1@domain.tld")
+        self._create_alias("alias1@domain.tld", "user1@domain.tld")
+        self._create_alias("alias2@domain.tld", "user1@domain.tld")
         self.client.logout()
-        self.client.login(username='reseller', password='toto')
+        self.client.login(username="reseller", password="toto")
         # Delete the admin -> resources should go back to the
         # reseller's pool
         self.ajax_post(
             reverse("admin:account_delete", args=[user.id]),
             {}
         )
-        self._check_limit('mailboxes', 1, 2)
-        self._check_limit('mailbox_aliases', 2, 2)
+        self._check_limit("mailboxes", 1, 2)
+        self._check_limit("mailbox_aliases", 2, 2)
 
     def test_change_role(self):
-        self._create_domain('domain.tld')
-        self._create_account('admin1@domain.tld', role='DomainAdmins')
-        user = User.objects.get(username='admin1@domain.tld')
+        self._create_domain("domain.tld")
+        self._create_account("admin1@domain.tld", role="DomainAdmins")
+        user = User.objects.get(username="admin1@domain.tld")
 
         # Give 1 mailbox and 2 aliases to the admin -> should work
         values = {
-            'username': user.username, 'role': user.role, 'quota_act': True,
-            'is_active': user.is_active, 'email': user.email,
-            'mailboxes_limit': 1, 'mailbox_aliases_limit': 2,
-            'language': 'en'
+            "username": user.username, "role": user.role, "quota_act": True,
+            "is_active": user.is_active, "email": user.email,
+            "mailboxes_limit": 1, "mailbox_aliases_limit": 2,
+            "language": "en"
         }
         self.ajax_post(
             reverse("admin:account_change", args=[user.id]),
             values
         )
-        self._check_limit('mailboxes', 1, 1)
-        self._check_limit('mailbox_aliases', 0, 0)
+        self._check_limit("mailboxes", 1, 1)
+        self._check_limit("mailbox_aliases", 0, 0)
 
         # Change admin role to SimpleUser -> resources should go back
         # to the reseller.
         values = {
-            'username': user.username, 'role': 'SimpleUsers',
-            'quota_act': True,
-            'is_active': user.is_active, 'email': user.email,
-            'language': 'en',
+            "username": user.username, "role": "SimpleUsers",
+            "quota_act": True,
+            "is_active": user.is_active, "email": user.email,
+            "language": "en",
         }
         self.ajax_post(
             reverse("admin:account_change", args=[user.id]),
             values
         )
-        self._check_limit('mailboxes', 1, 2)
-        self._check_limit('mailbox_aliases', 0, 2)
+        self._check_limit("mailboxes", 1, 2)
+        self._check_limit("mailbox_aliases", 0, 2)
 
     def test_allocate_too_much(self):
-        self._create_domain('domain.tld')
-        self._create_account('admin1@domain.tld', role='DomainAdmins')
-        user = User.objects.get(username='admin1@domain.tld')
+        self._create_domain("domain.tld")
+        self._create_account("admin1@domain.tld", role="DomainAdmins")
+        user = User.objects.get(username="admin1@domain.tld")
 
         # Give 2 mailboxes and 3 aliases to the admin -> should fail.
         values = {
-            'username': user.username, 'role': user.role, 'quota_act': True,
-            'is_active': user.is_active, 'email': user.email,
-            'mailboxes_limit': 2, 'mailbox_aliases_limit': 3,
-            'language': 'en'
+            "username": user.username, "role": user.role, "quota_act": True,
+            "is_active": user.is_active, "email": user.email,
+            "mailboxes_limit": 2, "mailbox_aliases_limit": 3,
+            "language": "en"
         }
         resp = self.ajax_post(
             reverse("admin:account_change", args=[user.id]),
             values, 424
         )
-        self.assertEqual(resp, 'Not enough resources')
-        self._check_limit('mailboxes', 1, 2)
-        self._check_limit('mailbox_aliases', 0, 2)
+        self.assertEqual(resp, "Not enough resources")
+        self._check_limit("mailboxes", 1, 2)
+        self._check_limit("mailbox_aliases", 0, 2)
diff --git a/modoboa/parameters/apps.py b/modoboa/parameters/apps.py
index cbf060639..f6edd84c9 100644
--- a/modoboa/parameters/apps.py
+++ b/modoboa/parameters/apps.py
@@ -4,4 +4,4 @@ from django.apps import AppConfig
 
 
 class ParametersConfig(AppConfig):
-    name = 'parameters'
+    name = "parameters"
diff --git a/modoboa/relaydomains/tests.py b/modoboa/relaydomains/tests.py
index 4f8ddecb7..888094a73 100644
--- a/modoboa/relaydomains/tests.py
+++ b/modoboa/relaydomains/tests.py
@@ -53,12 +53,12 @@ class Operations(object):
             "default_mailbox_quota": domain.default_mailbox_quota
         }
         aliases = [alias.name for alias in domain.domainalias_set.all()]
-        if optype == 'add':
+        if optype == "add":
             aliases.append(name)
         else:
             aliases.remove(name)
         for cpt, alias in enumerate(aliases):
-            fname = 'aliases' if not cpt else 'aliases_%d' % cpt
+            fname = "aliases" if not cpt else "aliases_%d" % cpt
             values[fname] = alias
         return self.ajax_post(
             reverse("admin:domain_change",
@@ -115,20 +115,20 @@ class RelayDomainsTestCase(ModoTestCase, Operations):
 
         FIXME: add a check for domain alias.
         """
-        self._create_relay_domain('relaydomain1.tld')
-        transport = tr_models.Transport.objects.get(pattern='relaydomain1.tld')
+        self._create_relay_domain("relaydomain1.tld")
+        transport = tr_models.Transport.objects.get(pattern="relaydomain1.tld")
         self.assertEqual(
-            transport._settings["relay_target_host"], 'external.host.tld')
+            transport._settings["relay_target_host"], "external.host.tld")
         self.assertEqual(
             transport._settings["relay_verify_recipients"], False)
 
-        resp = self._create_relay_domain('test.com', 400)
-        self.assertEqual(resp['form_errors']['name'][0],
-                         'Domain with this Name already exists.')
-        resp = self._create_relay_domain('relaydomainalias.tld', 400)
+        resp = self._create_relay_domain("test.com", 400)
+        self.assertEqual(resp["form_errors"]["name"][0],
+                         "Domain with this Name already exists.")
+        resp = self._create_relay_domain("relaydomainalias.tld", 400)
         self.assertEqual(
-            resp['form_errors']['name'][0],
-            'A domain alias with this name already exists'
+            resp["form_errors"]["name"][0],
+            "A domain alias with this name already exists"
         )
 
     def test_create_relaydomainalias(self):
@@ -140,21 +140,21 @@ class RelayDomainsTestCase(ModoTestCase, Operations):
         FIXME: add a check for domain alias.
         """
         self._relay_domain_alias_operation(
-            'add', self.dom, 'relaydomainalias1.tld'
+            "add", self.dom, "relaydomainalias1.tld"
         )
         resp = self._relay_domain_alias_operation(
-            'add', self.dom, 'test.com', 400
+            "add", self.dom, "test.com", 400
         )
         self.assertEqual(
-            resp['form_errors']['aliases_2'][0],
-            'A domain with this name already exists'
+            resp["form_errors"]["aliases_2"][0],
+            "A domain with this name already exists"
         )
         resp = self._relay_domain_alias_operation(
-            'add', self.dom, self.dom.name, 400
+            "add", self.dom, self.dom.name, 400
         )
         self.assertEqual(
-            resp['form_errors']['aliases_2'][0],
-            'A domain with this name already exists'
+            resp["form_errors"]["aliases_2"][0],
+            "A domain with this name already exists"
         )
 
     def test_edit_relaydomain(self):
@@ -238,12 +238,12 @@ class RelayDomainsTestCase(ModoTestCase, Operations):
             "quota": 0, "default_mailbox_quota": 0
         }
         self.ajax_post(
-            reverse('admin:domain_change', args=[self.dom.id]),
+            reverse("admin:domain_change", args=[self.dom.id]),
             values
         )
-        admin_models.DomainAlias.objects.get(name='relaydomainalias.net')
+        admin_models.DomainAlias.objects.get(name="relaydomainalias.net")
         with self.assertRaises(admin_models.DomainAlias.DoesNotExist):
-            admin_models.DomainAlias.objects.get(name='relaydomainalias.tld')
+            admin_models.DomainAlias.objects.get(name="relaydomainalias.tld")
 
     def test_delete_relaydomain(self):
         """Test the removal of a relay domain."""
@@ -316,7 +316,7 @@ class LimitsTestCase(ModoTestCase, Operations):
                 "deflt_user_{0}_limit".format(name), 2, app="limits")
         cls.localconfig.save()
         cls.user = UserFactory.create(
-            username='reseller', groups=('Resellers',)
+            username="reseller", groups=("Resellers",)
         )
 
     def setUp(self):
@@ -326,38 +326,38 @@ class LimitsTestCase(ModoTestCase, Operations):
 
     def test_relay_domains_limit(self):
         self._create_relay_domain(
-            'relaydomain1.tld', quota=1, default_mailbox_quota=1)
-        self._check_limit('domains', 1, 2)
+            "relaydomain1.tld", quota=1, default_mailbox_quota=1)
+        self._check_limit("domains", 1, 2)
         self._create_relay_domain(
-            'relaydomain2.tld', quota=1, default_mailbox_quota=1)
-        self._check_limit('domains', 2, 2)
-        self._create_relay_domain('relaydomain3.tld', 403)
-        self._check_limit('domains', 2, 2)
-        domid = admin_models.Domain.objects.get(name='relaydomain2.tld').id
+            "relaydomain2.tld", quota=1, default_mailbox_quota=1)
+        self._check_limit("domains", 2, 2)
+        self._create_relay_domain("relaydomain3.tld", 403)
+        self._check_limit("domains", 2, 2)
+        domid = admin_models.Domain.objects.get(name="relaydomain2.tld").id
         self.ajax_post(
-            reverse('admin:domain_delete', args=[domid]), {})
-        self._check_limit('domains', 1, 2)
+            reverse("admin:domain_delete", args=[domid]), {})
+        self._check_limit("domains", 1, 2)
 
     def test_relay_domain_aliases_limit(self):
         self._create_relay_domain(
-            'relaydomain1.tld', quota=1, default_mailbox_quota=1)
+            "relaydomain1.tld", quota=1, default_mailbox_quota=1)
         domain = admin_models.Domain.objects.get(name="relaydomain1.tld")
         self._relay_domain_alias_operation(
-            'add', domain, 'relay-domain-alias1.tld'
+            "add", domain, "relay-domain-alias1.tld"
         )
-        self._check_limit('domain_aliases', 1, 2)
+        self._check_limit("domain_aliases", 1, 2)
         self._relay_domain_alias_operation(
-            'add', domain, 'relay-domain-alias2.tld'
+            "add", domain, "relay-domain-alias2.tld"
         )
-        self._check_limit('domain_aliases', 2, 2)
+        self._check_limit("domain_aliases", 2, 2)
         self._relay_domain_alias_operation(
-            'add', domain, 'relay-domain-alias3.tld', 403
+            "add", domain, "relay-domain-alias3.tld", 403
         )
-        self._check_limit('domain_aliases', 2, 2)
+        self._check_limit("domain_aliases", 2, 2)
         self._relay_domain_alias_operation(
-            'delete', domain, 'relay-domain-alias2.tld'
+            "delete", domain, "relay-domain-alias2.tld"
         )
-        self._check_limit('domain_aliases', 1, 2)
+        self._check_limit("domain_aliases", 1, 2)
 
 
 class MapFilesTestCase(MapFilesTestCaseMixin, TestCase):
diff --git a/modoboa/test_settings.py b/modoboa/test_settings.py
index 69738187b..781bc5705 100644
--- a/modoboa/test_settings.py
+++ b/modoboa/test_settings.py
@@ -7,46 +7,46 @@ import os
 # Database
 # https://docs.djangoproject.com/en/1.11/ref/settings/#databases
 
-DB = os.environ.get('DB', 'POSTGRESQL')
+DB = os.environ.get("DB", "POSTGRESQL")
 
-if DB == 'MYSQL':
+if DB == "MYSQL":
     DATABASES = {
-        'default': {
-            'ENGINE': 'django.db.backends.mysql',
-            'NAME': 'modoboa',
-            'USER': 'root',
-            'PASSWORD': '',
-            'HOST': 'localhost',
-            'PORT': '',
-            'ATOMIC_REQUESTS': True,
+        "default": {
+            "ENGINE": "django.db.backends.mysql",
+            "NAME": "modoboa",
+            "USER": "root",
+            "PASSWORD": "",
+            "HOST": "localhost",
+            "PORT": "",
+            "ATOMIC_REQUESTS": True,
             # MySQL's Strict Mode fixes many data integrity problems in MySQL,
             # such as data truncation upon insertion, by escalating warnings
             # into errors. It is strongly recommended you activate it.
             # MySQL >= 5.7 set STRICT_TRANS_TABLES by default
             # See: https://docs.djangoproject.com/en/1.11/ref/databases/#mysql-sql-mode
-            'OPTIONS': {
-                'init_command': 'SET sql_mode=\'STRICT_TRANS_TABLES\'',
+            "OPTIONS": {
+                "init_command": 'SET sql_mode=\'STRICT_TRANS_TABLES\'',
             },
         },
     }
-elif DB == 'SQLITE':
+elif DB == "SQLITE":
     DATABASES = {
-        'default': {
-            'ENGINE': 'django.db.backends.sqlite3',
-            'NAME': 'modoboa.db',
-            'PORT': '',
-            'ATOMIC_REQUESTS': True,
+        "default": {
+            "ENGINE": "django.db.backends.sqlite3",
+            "NAME": "modoboa.db",
+            "PORT": "",
+            "ATOMIC_REQUESTS": True,
         },
     }
 else:
     DATABASES = {
-        'default': {
-            'ENGINE': 'django.db.backends.postgresql',
-            'NAME': 'modoboa',
-            'USER': 'postgres',
-            'PASSWORD': '',
-            'HOST': 'localhost',
-            'PORT': '',
-            'ATOMIC_REQUESTS': True,
+        "default": {
+            "ENGINE": "django.db.backends.postgresql",
+            "NAME": "modoboa",
+            "USER": "postgres",
+            "PASSWORD": "",
+            "HOST": "localhost",
+            "PORT": "",
+            "ATOMIC_REQUESTS": True,
         },
     }
diff --git a/modoboa/transport/apps.py b/modoboa/transport/apps.py
index 7162f121b..f7d87dd17 100644
--- a/modoboa/transport/apps.py
+++ b/modoboa/transport/apps.py
@@ -4,7 +4,7 @@ from django.apps import AppConfig
 
 
 class TransportConfig(AppConfig):
-    name = 'modoboa.transport'
+    name = "modoboa.transport"
 
     def ready(self):
         from . import handlers
diff --git a/modoboa/urls.py b/modoboa/urls.py
index 92584b7ba..2effc0145 100644
--- a/modoboa/urls.py
+++ b/modoboa/urls.py
@@ -17,17 +17,17 @@ from modoboa.core import signals as core_signals
 from modoboa.core import views as core_views
 from modoboa.core.extensions import exts_pool
 
-API_TITLE = 'Modoboa API'
+API_TITLE = "Modoboa API"
 
 urlpatterns = [
-    url(r'^jsi18n/$', JavaScriptCatalog.as_view(), name='javascript-catalog'),
+    url(r'^jsi18n/$', JavaScriptCatalog.as_view(), name="javascript-catalog"),
     url(r'^ckeditor/upload/', login_required(cku_views.upload),
         name="ckeditor_upload"),
     url(r'^ckeditor/browse/', login_required(cku_views.browse),
         name="ckeditor_browse"),
-    url('', include('modoboa.core.urls', namespace="core")),
-    url('^user/forward/', forward, name="user_forward"),
-    url('admin/', include('modoboa.admin.urls', namespace="admin")),
+    url("", include("modoboa.core.urls", namespace="core")),
+    url("^user/forward/", forward, name="user_forward"),
+    url("admin/", include("modoboa.admin.urls", namespace="admin")),
     # No namespace
     url(r'^accounts/password_reset/$', core_views.password_reset,
         name="password_reset"),
diff --git a/test_project/test_project/settings.py b/test_project/test_project/settings.py
index ca0df91f2..ba4356121 100644
--- a/test_project/test_project/settings.py
+++ b/test_project/test_project/settings.py
@@ -26,16 +26,16 @@ BASE_DIR = os.path.realpath(os.path.dirname(os.path.dirname(__file__)))
 # See https://docs.djangoproject.com/en/1.11/howto/deployment/checklist/
 
 # SECURITY WARNING: keep the secret key used in production secret!
-SECRET_KEY = '!8o(-dbbl3e+*bh7nx-^xysdt)1gso*%@4ze4-9_9o+i&amp;t--u_'
+SECRET_KEY = "!8o(-dbbl3e+*bh7nx-^xysdt)1gso*%@4ze4-9_9o+i&amp;t--u_"
 
 # SECURITY WARNING: don't run with debug turned on in production!
-DEBUG = 'DEBUG' in os.environ
+DEBUG = "DEBUG" in os.environ
 
 TEMPLATE_DEBUG = DEBUG
 
 ALLOWED_HOSTS = [
-    '127.0.0.1',
-    'localhost',
+    "127.0.0.1",
+    "localhost",
 ]
 
 SITE_ID = 1
@@ -47,57 +47,57 @@ X_FRAME_OPTIONS = "SAMEORIGIN"
 # Application definition
 
 INSTALLED_APPS = (
-    'django.contrib.auth',
-    'django.contrib.contenttypes',
-    'django.contrib.sessions',
-    'django.contrib.messages',
-    'django.contrib.sites',
-    'django.contrib.staticfiles',
-    'reversion',
-    'ckeditor',
-    'ckeditor_uploader',
-    'rest_framework',
-    'rest_framework.authtoken',
+    "django.contrib.auth",
+    "django.contrib.contenttypes",
+    "django.contrib.sessions",
+    "django.contrib.messages",
+    "django.contrib.sites",
+    "django.contrib.staticfiles",
+    "reversion",
+    "ckeditor",
+    "ckeditor_uploader",
+    "rest_framework",
+    "rest_framework.authtoken",
 )
 
 # A dedicated place to register Modoboa applications
 # Do not delete it.
 # Do not change the order.
 MODOBOA_APPS = (
-    'modoboa',
-    'modoboa.core',
-    'modoboa.lib',
-    'modoboa.admin',
-    'modoboa.transport',
-    'modoboa.relaydomains',
-    'modoboa.limits',
-    'modoboa.parameters',
+    "modoboa",
+    "modoboa.core",
+    "modoboa.lib",
+    "modoboa.admin",
+    "modoboa.transport",
+    "modoboa.relaydomains",
+    "modoboa.limits",
+    "modoboa.parameters",
     # Modoboa extensions here.
 )
 
 INSTALLED_APPS += MODOBOA_APPS
 
-AUTH_USER_MODEL = 'core.User'
+AUTH_USER_MODEL = "core.User"
 
 MIDDLEWARE = (
-    'x_forwarded_for.middleware.XForwardedForMiddleware',
-    'django.contrib.sessions.middleware.SessionMiddleware',
-    'django.middleware.common.CommonMiddleware',
-    'django.middleware.csrf.CsrfViewMiddleware',
-    'django.contrib.auth.middleware.AuthenticationMiddleware',
-    'django.contrib.messages.middleware.MessageMiddleware',
-    'django.middleware.locale.LocaleMiddleware',
-    'django.middleware.clickjacking.XFrameOptionsMiddleware',
-    'modoboa.core.middleware.LocalConfigMiddleware',
-    'modoboa.lib.middleware.AjaxLoginRedirect',
-    'modoboa.lib.middleware.CommonExceptionCatcher',
-    'modoboa.lib.middleware.RequestCatcherMiddleware',
+    "x_forwarded_for.middleware.XForwardedForMiddleware",
+    "django.contrib.sessions.middleware.SessionMiddleware",
+    "django.middleware.common.CommonMiddleware",
+    "django.middleware.csrf.CsrfViewMiddleware",
+    "django.contrib.auth.middleware.AuthenticationMiddleware",
+    "django.contrib.messages.middleware.MessageMiddleware",
+    "django.middleware.locale.LocaleMiddleware",
+    "django.middleware.clickjacking.XFrameOptionsMiddleware",
+    "modoboa.core.middleware.LocalConfigMiddleware",
+    "modoboa.lib.middleware.AjaxLoginRedirect",
+    "modoboa.lib.middleware.CommonExceptionCatcher",
+    "modoboa.lib.middleware.RequestCatcherMiddleware",
 )
 
 AUTHENTICATION_BACKENDS = (
     # 'modoboa.lib.authbackends.LDAPBackend',
     # 'modoboa.lib.authbackends.SMTPBackend',
-    'django.contrib.auth.backends.ModelBackend',
+    "django.contrib.auth.backends.ModelBackend",
 )
 
 # SMTP authentication
@@ -108,37 +108,37 @@ AUTHENTICATION_BACKENDS = (
 
 TEMPLATES = [
     {
-        'BACKEND': 'django.template.backends.django.DjangoTemplates',
-        'DIRS': [],
-        'APP_DIRS': True,
-        'OPTIONS': {
-            'context_processors': [
-                'django.template.context_processors.debug',
-                'django.template.context_processors.request',
-                'django.contrib.auth.context_processors.auth',
-                'django.template.context_processors.i18n',
-                'django.template.context_processors.media',
-                'django.template.context_processors.static',
-                'django.template.context_processors.tz',
-                'django.contrib.messages.context_processors.messages',
-                'modoboa.core.context_processors.top_notifications',
+        "BACKEND": "django.template.backends.django.DjangoTemplates",
+        "DIRS": [],
+        "APP_DIRS": True,
+        "OPTIONS": {
+            "context_processors": [
+                "django.template.context_processors.debug",
+                "django.template.context_processors.request",
+                "django.contrib.auth.context_processors.auth",
+                "django.template.context_processors.i18n",
+                "django.template.context_processors.media",
+                "django.template.context_processors.static",
+                "django.template.context_processors.tz",
+                "django.contrib.messages.context_processors.messages",
+                "modoboa.core.context_processors.top_notifications",
             ],
-            'debug': TEMPLATE_DEBUG,
+            "debug": TEMPLATE_DEBUG,
         },
     },
 ]
 
-ROOT_URLCONF = 'test_project.urls'
+ROOT_URLCONF = "test_project.urls"
 
-WSGI_APPLICATION = 'test_project.wsgi.application'
+WSGI_APPLICATION = "test_project.wsgi.application"
 
 
 # Internationalization
 # https://docs.djangoproject.com/en/1.11/topics/i18n/
 
-LANGUAGE_CODE = 'en-us'
+LANGUAGE_CODE = "en-us"
 
-TIME_ZONE = 'UTC'
+TIME_ZONE = "UTC"
 
 USE_I18N = True
 
@@ -149,21 +149,21 @@ USE_TZ = True
 # Static files (CSS, JavaScript, Images)
 # https://docs.djangoproject.com/en/1.11/howto/static-files/
 
-STATIC_URL = '/sitestatic/'
-STATIC_ROOT = os.path.join(BASE_DIR, 'sitestatic')
+STATIC_URL = "/sitestatic/"
+STATIC_ROOT = os.path.join(BASE_DIR, "sitestatic")
 STATICFILES_DIRS = (
-    os.path.join(BASE_DIR, '..', 'modoboa', 'bower_components'),
+    os.path.join(BASE_DIR, "..", "modoboa", "bower_components"),
 )
 
-MEDIA_URL = '/media/'
-MEDIA_ROOT = os.path.join(BASE_DIR, 'media')
+MEDIA_URL = "/media/"
+MEDIA_ROOT = os.path.join(BASE_DIR, "media")
 
 # Rest framework settings
 
 REST_FRAMEWORK = {
-    'DEFAULT_AUTHENTICATION_CLASSES': (
-        'rest_framework.authentication.TokenAuthentication',
-        'rest_framework.authentication.SessionAuthentication',
+    "DEFAULT_AUTHENTICATION_CLASSES": (
+        "rest_framework.authentication.TokenAuthentication",
+        "rest_framework.authentication.SessionAuthentication",
     ),
 }
 
@@ -172,31 +172,31 @@ REST_FRAMEWORK = {
 
 # DOVECOT_LOOKUP_PATH = ('/path/to/dovecot', )
 
-MODOBOA_API_URL = 'https://api.modoboa.org/1/'
+MODOBOA_API_URL = "https://api.modoboa.org/1/"
 
 # Password validation
 # https://docs.djangoproject.com/en/1.11/ref/settings/#auth-password-validators
 
 AUTH_PASSWORD_VALIDATORS = [
     {
-        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
+        "NAME": "django.contrib.auth.password_validation.UserAttributeSimilarityValidator",
     },
     {
-        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
+        "NAME": "django.contrib.auth.password_validation.MinimumLengthValidator",
     },
     {
-        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
+        "NAME": "django.contrib.auth.password_validation.CommonPasswordValidator",
     },
     {
-        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
+        "NAME": "django.contrib.auth.password_validation.NumericPasswordValidator",
     },
     {
-        'NAME': 'modoboa.core.password_validation.ComplexityValidator',
-        'OPTIONS': {
-            'upper': 1,
-            'lower': 1,
-            'digits': 1,
-            'specials': 0
+        "NAME": "modoboa.core.password_validation.ComplexityValidator",
+        "OPTIONS": {
+            "upper": 1,
+            "lower": 1,
+            "digits": 1,
+            "specials": 0
         }
     },
 ]
@@ -214,21 +214,21 @@ CKEDITOR_BROWSE_SHOW_DIRS = True
 CKEDITOR_ALLOW_NONIMAGE_FILES = False
 
 CKEDITOR_CONFIGS = {
-    'default': {
-        'allowedContent': True,
-        'toolbar': 'Modoboa',
-        'width': None,
-        'toolbar_Modoboa': [
-            ['Bold', 'Italic', 'Underline'],
-            ['JustifyLeft', 'JustifyCenter', 'JustifyRight', 'JustifyBlock'],
-            ['BidiLtr', 'BidiRtl', 'Language'],
-            ['NumberedList', 'BulletedList', '-', 'Outdent', 'Indent'],
-            ['Undo', 'Redo'],
-            ['Link', 'Unlink', 'Anchor', '-', 'Smiley'],
-            ['TextColor', 'BGColor', '-', 'Source'],
-            ['Font', 'FontSize'],
-            ['Image', ],
-            ['SpellChecker']
+    "default": {
+        "allowedContent": True,
+        "toolbar": "Modoboa",
+        "width": None,
+        "toolbar_Modoboa": [
+            ["Bold", "Italic", "Underline"],
+            ["JustifyLeft", "JustifyCenter", "JustifyRight", "JustifyBlock"],
+            ["BidiLtr", "BidiRtl", "Language"],
+            ["NumberedList", "BulletedList", "-", "Outdent", "Indent"],
+            ["Undo", "Redo"],
+            ["Link", "Unlink", "Anchor", "-", "Smiley"],
+            ["TextColor", "BGColor", "-", "Source"],
+            ["Font", "FontSize"],
+            ["Image", ],
+            ["SpellChecker"]
         ],
     },
 }
@@ -236,33 +236,33 @@ CKEDITOR_CONFIGS = {
 # Logging configuration
 
 LOGGING = {
-    'version': 1,
-    'disable_existing_loggers': False,
-    'formatters': {
-        'syslog': {
-            'format': '%(name)s: %(levelname)s %(message)s'
+    "version": 1,
+    "disable_existing_loggers": False,
+    "formatters": {
+        "syslog": {
+            "format": "%(name)s: %(levelname)s %(message)s"
         },
     },
-    'handlers': {
-        'syslog-auth': {
-            'class': 'logging.handlers.SysLogHandler',
-            'facility': SysLogHandler.LOG_AUTH,
-            'formatter': 'syslog'
+    "handlers": {
+        "syslog-auth": {
+            "class": "logging.handlers.SysLogHandler",
+            "facility": SysLogHandler.LOG_AUTH,
+            "formatter": "syslog"
         },
-        'modoboa': {
-            'class': 'modoboa.core.loggers.SQLHandler',
+        "modoboa": {
+            "class": "modoboa.core.loggers.SQLHandler",
         }
     },
-    'loggers': {
-        'modoboa.auth': {
-            'handlers': ['syslog-auth', 'modoboa'],
-            'level': 'INFO',
-            'propagate': False
+    "loggers": {
+        "modoboa.auth": {
+            "handlers": ["syslog-auth", "modoboa"],
+            "level": "INFO",
+            "propagate": False
         },
-        'modoboa.admin': {
-            'handlers': ['modoboa'],
-            'level': 'INFO',
-            'propagate': False
+        "modoboa.admin": {
+            "handlers": ["modoboa"],
+            "level": "INFO",
+            "propagate": False
         }
     }
 }
diff --git a/tests.py b/tests.py
index 69a5e184f..07180185f 100644
--- a/tests.py
+++ b/tests.py
@@ -25,7 +25,7 @@ class DeployTest(unittest.TestCase):
         cmd = (
             "modoboa-admin.py deploy --collectstatic "
             "--dburl %s --domain %s --admin-username admin %s"
-            % (dburl, 'localhost', self.projname)
+            % (dburl, "localhost", self.projname)
         )
         code, output = exec_cmd(cmd, cwd=self.workdir)
         self.assertEqual(code, 0)