diff --git a/modoboa/admin/forms/account.py b/modoboa/admin/forms/account.py
index 19effd8ab..db0a312ce 100644
--- a/modoboa/admin/forms/account.py
+++ b/modoboa/admin/forms/account.py
@@ -6,7 +6,7 @@ from collections import OrderedDict
 from functools import reduce
 
 from django import forms
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.http import QueryDict
 from django.utils.translation import ugettext as _, ugettext_lazy
 
diff --git a/modoboa/admin/forms/domain.py b/modoboa/admin/forms/domain.py
index 23e2e9343..558b6e89f 100644
--- a/modoboa/admin/forms/domain.py
+++ b/modoboa/admin/forms/domain.py
@@ -5,7 +5,7 @@ from __future__ import unicode_literals
 from functools import reduce
 
 from django import forms
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.http import QueryDict
 from django.utils.translation import ugettext as _, ugettext_lazy
 from django.utils.encoding import force_text
diff --git a/modoboa/admin/handlers.py b/modoboa/admin/handlers.py
index c51e01b27..da360c6d8 100644
--- a/modoboa/admin/handlers.py
+++ b/modoboa/admin/handlers.py
@@ -2,7 +2,7 @@
 
 from __future__ import unicode_literals
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.db.models import signals
 from django.dispatch import receiver
 from django.utils.translation import ugettext as _
diff --git a/modoboa/admin/migrations/0001_initial.py b/modoboa/admin/migrations/0001_initial.py
index ec5eb96bb..9be649089 100644
--- a/modoboa/admin/migrations/0001_initial.py
+++ b/modoboa/admin/migrations/0001_initial.py
@@ -31,8 +31,8 @@ class Migration(migrations.Migration):
             fields=[
                 ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                 ('address', models.EmailField(max_length=75)),
-                ('alias', models.ForeignKey(to='admin.Alias')),
-                ('r_alias', models.ForeignKey(related_name='alias_recipient_aliases', blank=True, to='admin.Alias', null=True)),
+                ('alias', models.ForeignKey(to='admin.Alias', on_delete=models.CASCADE)),
+                ('r_alias', models.ForeignKey(related_name='alias_recipient_aliases', blank=True, to='admin.Alias', null=True, on_delete=models.CASCADE)),
             ],
             options={
                 'db_table': 'modoboa_admin_aliasrecipient',
@@ -85,7 +85,7 @@ class Migration(migrations.Migration):
                 ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                 ('type', models.CharField(max_length=20, choices=[(b'rename', b'rename'), (b'delete', b'delete')])),
                 ('argument', models.TextField()),
-                ('mailbox', models.ForeignKey(blank=True, to='admin.Mailbox', null=True)),
+                ('mailbox', models.ForeignKey(blank=True, to='admin.Mailbox', null=True, on_delete=models.CASCADE)),
             ],
             options={
             },
@@ -116,43 +116,43 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name='mailbox',
             name='dates',
-            field=models.ForeignKey(to='admin.ObjectDates'),
+            field=models.ForeignKey(to='admin.ObjectDates', on_delete=models.CASCADE),
             preserve_default=True,
         ),
         migrations.AddField(
             model_name='mailbox',
             name='domain',
-            field=models.ForeignKey(to='admin.Domain'),
+            field=models.ForeignKey(to='admin.Domain', on_delete=models.CASCADE),
             preserve_default=True,
         ),
         migrations.AddField(
             model_name='mailbox',
             name='user',
-            field=models.OneToOneField(to=settings.AUTH_USER_MODEL),
+            field=models.OneToOneField(to=settings.AUTH_USER_MODEL, on_delete=models.CASCADE),
             preserve_default=True,
         ),
         migrations.AddField(
             model_name='domainalias',
             name='dates',
-            field=models.ForeignKey(to='admin.ObjectDates'),
+            field=models.ForeignKey(to='admin.ObjectDates', on_delete=models.CASCADE),
             preserve_default=True,
         ),
         migrations.AddField(
             model_name='domainalias',
             name='target',
-            field=models.ForeignKey(verbose_name='target', to='admin.Domain', help_text='The domain this alias points to'),
+            field=models.ForeignKey(verbose_name='target', to='admin.Domain', help_text='The domain this alias points to', on_delete=models.CASCADE),
             preserve_default=True,
         ),
         migrations.AddField(
             model_name='domain',
             name='dates',
-            field=models.ForeignKey(to='admin.ObjectDates'),
+            field=models.ForeignKey(to='admin.ObjectDates', on_delete=models.CASCADE),
             preserve_default=True,
         ),
         migrations.AddField(
             model_name='aliasrecipient',
             name='r_mailbox',
-            field=models.ForeignKey(blank=True, to='admin.Mailbox', null=True),
+            field=models.ForeignKey(blank=True, to='admin.Mailbox', null=True, on_delete=models.CASCADE),
             preserve_default=True,
         ),
         migrations.AlterUniqueTogether(
@@ -162,13 +162,13 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name='alias',
             name='dates',
-            field=models.ForeignKey(to='admin.ObjectDates'),
+            field=models.ForeignKey(to='admin.ObjectDates', on_delete=models.CASCADE),
             preserve_default=True,
         ),
         migrations.AddField(
             model_name='alias',
             name='domain',
-            field=models.ForeignKey(to='admin.Domain', null=True),
+            field=models.ForeignKey(to='admin.Domain', null=True, on_delete=models.CASCADE),
             preserve_default=True,
         ),
         migrations.AlterUniqueTogether(
diff --git a/modoboa/admin/models/alias.py b/modoboa/admin/models/alias.py
index 59b796725..225ed9e78 100644
--- a/modoboa/admin/models/alias.py
+++ b/modoboa/admin/models/alias.py
@@ -5,7 +5,7 @@ from __future__ import unicode_literals
 import hashlib
 import random
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.db import models
 from django.utils.encoding import (
     python_2_unicode_compatible, smart_text, force_str, force_bytes
@@ -37,7 +37,7 @@ class Alias(AdminObject):
             "The alias address."
         )
     )
-    domain = models.ForeignKey(Domain, null=True)
+    domain = models.ForeignKey(Domain, null=True, on_delete=models.CASCADE)
     enabled = models.BooleanField(
         ugettext_lazy("enabled"),
         help_text=ugettext_lazy("Check to activate this alias"),
@@ -210,13 +210,15 @@ class AliasRecipient(models.Model):
     """An alias recipient."""
 
     address = models.EmailField()
-    alias = models.ForeignKey(Alias)
+    alias = models.ForeignKey(Alias, on_delete=models.CASCADE)
 
     # if recipient is a local mailbox
-    r_mailbox = models.ForeignKey(Mailbox, blank=True, null=True)
+    r_mailbox = models.ForeignKey(Mailbox, blank=True, null=True,
+                                  on_delete=models.CASCADE)
     # if recipient is a local alias
     r_alias = models.ForeignKey(
-        Alias, related_name="alias_recipient_aliases", blank=True, null=True)
+        Alias, related_name="alias_recipient_aliases", blank=True, null=True,
+        on_delete=models.CASCADE)
 
     class Meta:
         app_label = "admin"
diff --git a/modoboa/admin/models/domain_alias.py b/modoboa/admin/models/domain_alias.py
index c9047886d..51ccfba69 100644
--- a/modoboa/admin/models/domain_alias.py
+++ b/modoboa/admin/models/domain_alias.py
@@ -40,7 +40,8 @@ class DomainAlias(AdminObject):
                             help_text=ugettext_lazy("The alias name"))
     target = models.ForeignKey(
         Domain, verbose_name=ugettext_lazy('target'),
-        help_text=ugettext_lazy("The domain this alias points to")
+        help_text=ugettext_lazy("The domain this alias points to"),
+        on_delete=models.CASCADE
     )
     enabled = models.BooleanField(
         ugettext_lazy('enabled'),
diff --git a/modoboa/admin/models/mailbox.py b/modoboa/admin/models/mailbox.py
index 1cf18320d..790cf9fbb 100644
--- a/modoboa/admin/models/mailbox.py
+++ b/modoboa/admin/models/mailbox.py
@@ -100,8 +100,8 @@ class Mailbox(AdminObject):
     )
     quota = models.PositiveIntegerField(default=0)
     use_domain_quota = models.BooleanField(default=False)
-    domain = models.ForeignKey(Domain)
-    user = models.OneToOneField(User)
+    domain = models.ForeignKey(Domain, on_delete=models.CASCADE)
+    user = models.OneToOneField(User, on_delete=models.CASCADE)
 
     objects = MailboxManager()
 
@@ -354,7 +354,7 @@ class SenderAddress(models.Model):
     """Extra sender address for Mailbox."""
 
     address = models.EmailField()
-    mailbox = models.ForeignKey(Mailbox)
+    mailbox = models.ForeignKey(Mailbox, on_delete=models.CASCADE)
 
     class Meta:
         app_label = "admin"
@@ -373,7 +373,8 @@ reversion.register(SenderAddress)
 class MailboxOperation(models.Model):
     """An operation on a mailbox."""
 
-    mailbox = models.ForeignKey(Mailbox, blank=True, null=True)
+    mailbox = models.ForeignKey(Mailbox, blank=True, null=True,
+                                on_delete=models.CASCADE)
     type = models.CharField(
         max_length=20, choices=(('rename', 'rename'), ('delete', 'delete'))
     )
diff --git a/modoboa/admin/models/mxrecord.py b/modoboa/admin/models/mxrecord.py
index b48645430..4a4f71e5b 100644
--- a/modoboa/admin/models/mxrecord.py
+++ b/modoboa/admin/models/mxrecord.py
@@ -58,7 +58,7 @@ class MXRecordManager(models.Manager):
 class MXRecord(models.Model):
     """A model used to store MX records for Domain."""
 
-    domain = models.ForeignKey("admin.Domain")
+    domain = models.ForeignKey("admin.Domain", on_delete=models.CASCADE)
     name = models.CharField(max_length=254)
     address = models.GenericIPAddressField()
     managed = models.BooleanField(default=False)
@@ -86,9 +86,9 @@ class DNSBLQuerySet(models.QuerySet):
 class DNSBLResult(models.Model):
     """Store a DNSBL query result."""
 
-    domain = models.ForeignKey("admin.Domain")
+    domain = models.ForeignKey("admin.Domain", on_delete=models.CASCADE)
     provider = models.CharField(max_length=254, db_index=True)
-    mx = models.ForeignKey(MXRecord)
+    mx = models.ForeignKey(MXRecord, on_delete=models.CASCADE)
     status = models.CharField(max_length=45, blank=True, db_index=True)
 
     objects = models.Manager.from_queryset(DNSBLQuerySet)()
diff --git a/modoboa/admin/templatetags/admin_tags.py b/modoboa/admin/templatetags/admin_tags.py
index 750ce39c3..202088157 100644
--- a/modoboa/admin/templatetags/admin_tags.py
+++ b/modoboa/admin/templatetags/admin_tags.py
@@ -5,7 +5,7 @@ from __future__ import unicode_literals
 from functools import reduce
 
 from django import template
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.template.loader import render_to_string
 from django.utils.safestring import mark_safe
 from django.utils.translation import ugettext as _, ugettext_lazy
diff --git a/modoboa/admin/tests/test_account.py b/modoboa/admin/tests/test_account.py
index acf1baf9d..3f6f2144d 100644
--- a/modoboa/admin/tests/test_account.py
+++ b/modoboa/admin/tests/test_account.py
@@ -4,7 +4,7 @@ from __future__ import unicode_literals
 
 from unittest import skipIf
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.test import override_settings
 
 from modoboa.core import factories as core_factories
diff --git a/modoboa/admin/tests/test_alias.py b/modoboa/admin/tests/test_alias.py
index 046b85275..3df90621d 100644
--- a/modoboa/admin/tests/test_alias.py
+++ b/modoboa/admin/tests/test_alias.py
@@ -4,7 +4,7 @@ from __future__ import unicode_literals
 
 """Admin test cases."""
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 
 from modoboa.core.models import User
 from modoboa.lib.tests import ModoTestCase
diff --git a/modoboa/admin/tests/test_api.py b/modoboa/admin/tests/test_api.py
index 3e897ce18..718adecc6 100644
--- a/modoboa/admin/tests/test_api.py
+++ b/modoboa/admin/tests/test_api.py
@@ -9,7 +9,7 @@ import json
 import dns.resolver
 from mock import patch
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 
 from rest_framework.authtoken.models import Token
 
diff --git a/modoboa/admin/tests/test_domain.py b/modoboa/admin/tests/test_domain.py
index b3eeabfeb..553a861a8 100644
--- a/modoboa/admin/tests/test_domain.py
+++ b/modoboa/admin/tests/test_domain.py
@@ -7,7 +7,7 @@ from __future__ import unicode_literals
 import dns.resolver
 from mock import patch
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 
 from modoboa.core import factories as core_factories
 from modoboa.core.models import User
diff --git a/modoboa/admin/tests/test_domain_alias.py b/modoboa/admin/tests/test_domain_alias.py
index 76f92fb16..5dd667702 100644
--- a/modoboa/admin/tests/test_domain_alias.py
+++ b/modoboa/admin/tests/test_domain_alias.py
@@ -2,7 +2,7 @@
 
 from __future__ import unicode_literals
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 
 from modoboa.lib.tests import ModoTestCase
 
diff --git a/modoboa/admin/tests/test_export.py b/modoboa/admin/tests/test_export.py
index f7ba5177f..c48e3486d 100644
--- a/modoboa/admin/tests/test_export.py
+++ b/modoboa/admin/tests/test_export.py
@@ -4,7 +4,7 @@
 
 from __future__ import unicode_literals
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.utils.encoding import force_text
 
 from modoboa.lib.tests import ModoTestCase
diff --git a/modoboa/admin/tests/test_import_.py b/modoboa/admin/tests/test_import_.py
index b40445f77..370c2087c 100644
--- a/modoboa/admin/tests/test_import_.py
+++ b/modoboa/admin/tests/test_import_.py
@@ -6,7 +6,7 @@ from mock import patch
 import dns.resolver
 
 from django.core.files.base import ContentFile
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 
 from modoboa.core import factories as core_factories
 from modoboa.core.models import User
diff --git a/modoboa/admin/tests/test_mailbox_operations.py b/modoboa/admin/tests/test_mailbox_operations.py
index 2f9a719ee..81c02de97 100644
--- a/modoboa/admin/tests/test_mailbox_operations.py
+++ b/modoboa/admin/tests/test_mailbox_operations.py
@@ -9,7 +9,7 @@ import tempfile
 import mock
 
 from django.core.management import call_command
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.test import override_settings
 
 from modoboa.lib.tests import ModoTestCase
diff --git a/modoboa/admin/tests/test_mx.py b/modoboa/admin/tests/test_mx.py
index 2e2a39b10..53d2a94c6 100644
--- a/modoboa/admin/tests/test_mx.py
+++ b/modoboa/admin/tests/test_mx.py
@@ -6,7 +6,7 @@ from mock import patch
 
 from django.core import mail
 from django.core import management
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.test import override_settings
 
 from modoboa.core import factories as core_factories
diff --git a/modoboa/admin/tests/test_password_schemes.py b/modoboa/admin/tests/test_password_schemes.py
index 160d1e0b2..277d202b9 100644
--- a/modoboa/admin/tests/test_password_schemes.py
+++ b/modoboa/admin/tests/test_password_schemes.py
@@ -1,6 +1,6 @@
 from __future__ import unicode_literals
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 
 from modoboa.core.models import User
 from modoboa.lib.tests import ModoTestCase
diff --git a/modoboa/admin/tests/test_user.py b/modoboa/admin/tests/test_user.py
index 2eccfc900..1c55760ff 100644
--- a/modoboa/admin/tests/test_user.py
+++ b/modoboa/admin/tests/test_user.py
@@ -2,7 +2,7 @@
 
 from __future__ import unicode_literals
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 
 from modoboa.core.models import User
 from modoboa.lib.tests import ModoTestCase
diff --git a/modoboa/admin/views/alias.py b/modoboa/admin/views/alias.py
index 20b1c4635..a7c97f58b 100644
--- a/modoboa/admin/views/alias.py
+++ b/modoboa/admin/views/alias.py
@@ -2,7 +2,7 @@
 
 from __future__ import unicode_literals
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.db import IntegrityError
 from django.shortcuts import render
 from django.utils.translation import ugettext as _, ungettext
diff --git a/modoboa/admin/views/domain.py b/modoboa/admin/views/domain.py
index 2fd0f777e..4618b294a 100644
--- a/modoboa/admin/views/domain.py
+++ b/modoboa/admin/views/domain.py
@@ -4,7 +4,7 @@ from __future__ import unicode_literals
 
 from functools import reduce
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.db.models import Sum
 from django.http import HttpResponseRedirect
 from django.shortcuts import render
diff --git a/modoboa/admin/views/export.py b/modoboa/admin/views/export.py
index 89e6dabb0..f916ea8c5 100644
--- a/modoboa/admin/views/export.py
+++ b/modoboa/admin/views/export.py
@@ -9,7 +9,7 @@ from rfc6266 import build_header
 from django.contrib.auth.decorators import (
     login_required, permission_required, user_passes_test
 )
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.http import HttpResponse
 from django.shortcuts import render
 from django.utils.translation import ugettext as _
diff --git a/modoboa/admin/views/import_.py b/modoboa/admin/views/import_.py
index 44921471c..1291b41ee 100644
--- a/modoboa/admin/views/import_.py
+++ b/modoboa/admin/views/import_.py
@@ -9,7 +9,7 @@ from io import StringIO
 from django.contrib.auth.decorators import (
     login_required, permission_required, user_passes_test
 )
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.db import transaction
 from django.shortcuts import render
 from django.utils.translation import ugettext as _
diff --git a/modoboa/core/app_settings.py b/modoboa/core/app_settings.py
index ee7e699f6..0f69de5ad 100644
--- a/modoboa/core/app_settings.py
+++ b/modoboa/core/app_settings.py
@@ -11,7 +11,7 @@ from django.contrib.auth import password_validation
 from modoboa.lib import fields as lib_fields
 from modoboa.lib.cryptutils import random_key
 from modoboa.lib.form_utils import (
-    YesNoField, SeparatorField, InlineRadioSelect
+    YesNoField, SeparatorField, HorizontalRadioSelect
 )
 from modoboa.parameters import forms as param_forms
 from modoboa.parameters import tools as param_tools
@@ -44,7 +44,7 @@ class GeneralParametersForm(param_forms.AdminParametersForm):
                  ('ldap', "LDAP")],
         initial="local",
         help_text=ugettext_lazy("The backend used for authentication"),
-        widget=InlineRadioSelect
+        widget=HorizontalRadioSelect()
     )
 
     password_scheme = forms.ChoiceField(
diff --git a/modoboa/core/handlers.py b/modoboa/core/handlers.py
index c146dc89f..6f6c43649 100644
--- a/modoboa/core/handlers.py
+++ b/modoboa/core/handlers.py
@@ -4,7 +4,7 @@ from __future__ import unicode_literals
 
 import logging
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.db.models import signals
 from django.dispatch import receiver
 from django.utils.encoding import smart_text
diff --git a/modoboa/core/middleware.py b/modoboa/core/middleware.py
index f8f66b403..df8f6939a 100644
--- a/modoboa/core/middleware.py
+++ b/modoboa/core/middleware.py
@@ -2,10 +2,12 @@
 
 from __future__ import unicode_literals
 
+from django.utils.deprecation import MiddlewareMixin
+
 from . import models
 
 
-class LocalConfigMiddleware(object):
+class LocalConfigMiddleware(MiddlewareMixin):
     """A middleware to inject LocalConfig into request."""
 
     def process_request(self, request):
diff --git a/modoboa/core/migrations/0001_initial.py b/modoboa/core/migrations/0001_initial.py
index 3824558f1..1be0eae38 100644
--- a/modoboa/core/migrations/0001_initial.py
+++ b/modoboa/core/migrations/0001_initial.py
@@ -67,8 +67,8 @@ class Migration(migrations.Migration):
                 ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                 ('object_id', models.PositiveIntegerField()),
                 ('is_owner', models.BooleanField(default=False)),
-                ('content_type', models.ForeignKey(to='contenttypes.ContentType')),
-                ('user', models.ForeignKey(to=settings.AUTH_USER_MODEL)),
+                ('content_type', models.ForeignKey(to='contenttypes.ContentType', on_delete=models.CASCADE)),
+                ('user', models.ForeignKey(to=settings.AUTH_USER_MODEL, on_delete=models.CASCADE)),
             ],
             options={
             },
diff --git a/modoboa/core/models.py b/modoboa/core/models.py
index 0d2b203f4..4750f645e 100644
--- a/modoboa/core/models.py
+++ b/modoboa/core/models.py
@@ -5,7 +5,7 @@ from __future__ import unicode_literals
 from email.header import Header
 import re
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.db import models
 from django.utils.encoding import (
     python_2_unicode_compatible, smart_bytes, smart_text, force_str
@@ -407,8 +407,8 @@ def populate_callback(user, group="SimpleUsers"):
 
 @python_2_unicode_compatible
 class ObjectAccess(models.Model):
-    user = models.ForeignKey(User)
-    content_type = models.ForeignKey(ContentType)
+    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')
     is_owner = models.BooleanField(default=False)
@@ -435,7 +435,7 @@ class LocalConfig(models.Model):
     """Store instance configuration here."""
 
     api_pk = models.PositiveIntegerField(null=True)
-    site = models.ForeignKey("sites.Site")
+    site = models.ForeignKey("sites.Site", on_delete=models.CASCADE)
 
     # API results cache
     api_versions = jsonfield.JSONField()
diff --git a/modoboa/core/templatetags/core_tags.py b/modoboa/core/templatetags/core_tags.py
index 44d0735a4..20017f015 100644
--- a/modoboa/core/templatetags/core_tags.py
+++ b/modoboa/core/templatetags/core_tags.py
@@ -10,7 +10,7 @@ import re
 
 from django import template
 from django.conf import settings
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.template.loader import render_to_string
 from django.utils import timezone
 from django.utils.encoding import smart_text
diff --git a/modoboa/core/tests/test_authentication.py b/modoboa/core/tests/test_authentication.py
index 22df9d964..08c7fb4dc 100644
--- a/modoboa/core/tests/test_authentication.py
+++ b/modoboa/core/tests/test_authentication.py
@@ -10,7 +10,7 @@ from unittest import skipIf
 from mock import patch
 
 from django.core import mail
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.test import override_settings
 
 from modoboa.lib.tests import ModoTestCase
diff --git a/modoboa/core/tests/test_core.py b/modoboa/core/tests/test_core.py
index 6ca505c39..5efa811c5 100644
--- a/modoboa/core/tests/test_core.py
+++ b/modoboa/core/tests/test_core.py
@@ -8,7 +8,7 @@ from dateutil.relativedelta import relativedelta
 from six import StringIO
 
 from django.core import management
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.test import TestCase
 from django.utils import timezone
 
diff --git a/modoboa/core/tests/test_ldap.py b/modoboa/core/tests/test_ldap.py
index d7b166594..2de9be271 100644
--- a/modoboa/core/tests/test_ldap.py
+++ b/modoboa/core/tests/test_ldap.py
@@ -4,7 +4,7 @@ from __future__ import unicode_literals
 
 from unittest import skipIf
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.test import override_settings
 from django.utils.functional import cached_property
 
diff --git a/modoboa/core/tests/test_views.py b/modoboa/core/tests/test_views.py
index 8e06bdfce..0c433c16b 100644
--- a/modoboa/core/tests/test_views.py
+++ b/modoboa/core/tests/test_views.py
@@ -5,7 +5,7 @@ from __future__ import unicode_literals
 from testfixtures import compare
 
 from django import forms
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 
 from modoboa.lib.tests import ModoTestCase
 from modoboa.parameters import forms as param_forms
diff --git a/modoboa/core/views/auth.py b/modoboa/core/views/auth.py
index 2ca28c56a..577263144 100644
--- a/modoboa/core/views/auth.py
+++ b/modoboa/core/views/auth.py
@@ -5,7 +5,7 @@ from __future__ import unicode_literals
 
 import logging
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.http import HttpResponse, HttpResponseRedirect
 from django.template.loader import render_to_string
 from django.utils import translation
diff --git a/modoboa/core/views/base.py b/modoboa/core/views/base.py
index 8d4634bf3..7b6291bac 100644
--- a/modoboa/core/views/base.py
+++ b/modoboa/core/views/base.py
@@ -2,7 +2,7 @@
 
 from __future__ import unicode_literals
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.utils.http import is_safe_url
 from django.views import generic
 
diff --git a/modoboa/lib/form_utils.py b/modoboa/lib/form_utils.py
index 9aa259ff7..b9065bc30 100644
--- a/modoboa/lib/form_utils.py
+++ b/modoboa/lib/form_utils.py
@@ -11,12 +11,8 @@ import re
 from django.forms import TypedChoiceField
 from django.forms.fields import Field
 from django.forms.widgets import RadioSelect
-from django.forms.widgets import RadioChoiceInput
 from django.shortcuts import render
-from django.utils.encoding import (
-    python_2_unicode_compatible, force_text, force_str)
-from django.utils.html import conditional_escape
-from django.utils.safestring import mark_safe
+from django.utils.encoding import force_str
 from django.utils.translation import ugettext as _, ugettext_lazy
 
 from modoboa.lib.exceptions import BadRequest
@@ -371,41 +367,9 @@ class TabForms(object):
 #
 
 
-@python_2_unicode_compatible
-class CustomRadioInput(RadioChoiceInput):
-    """Custom radio input."""
-
-    def __str__(self):
-        if "id" in self.attrs:
-            label_for = ' for="%s"' % self.attrs["id"]
-        else:
-            label_for = ""
-        choice_label = conditional_escape(force_text(self.choice_label))
-        return mark_safe(
-            "<label class='radio-inline' %s>%s %s</label>"
-            % (label_for, self.tag(), choice_label)
-        )
-
-
-class InlineRadioRenderer(RadioSelect.renderer):
-    """Custom inline radio renderer."""
-
-    def __iter__(self):
-        for i, choice in enumerate(self.choices):
-            yield CustomRadioInput(
-                self.name, self.value, self.attrs.copy(), choice, i
-            )
-
-    def render(self):
-        return mark_safe(
-            u"\n".join([u"%s\n" % force_text(w) for w in self])
-        )
-
-
-class InlineRadioSelect(RadioSelect):
-    """Custom inline radio widget."""
-
-    renderer = InlineRadioRenderer
+class HorizontalRadioSelect(RadioSelect):
+    template_name = "common/horizontal_select.html"
+    option_template_name = "common/horizontal_select_option.html"
 
 
 class SeparatorField(Field):
@@ -426,7 +390,7 @@ class YesNoField(TypedChoiceField):
                 (True, ugettext_lazy("Yes")),
                 (False, ugettext_lazy("No"))
             ),
-            "widget": InlineRadioSelect,
+            "widget": HorizontalRadioSelect(),
             "coerce": lambda x: x == "True"
         })
         super(YesNoField, self).__init__(*args, **kwargs)
diff --git a/modoboa/lib/middleware.py b/modoboa/lib/middleware.py
index 6fd7c77f2..684726d65 100644
--- a/modoboa/lib/middleware.py
+++ b/modoboa/lib/middleware.py
@@ -6,6 +6,7 @@ from __future__ import unicode_literals
 
 from django.http import HttpResponseRedirect
 from django.utils.encoding import smart_text
+from django.utils.deprecation import MiddlewareMixin
 
 from modoboa.lib.exceptions import ModoboaException
 from modoboa.lib import signals as lib_signals
@@ -14,7 +15,7 @@ from modoboa.lib.web_utils import (
 )
 
 
-class AjaxLoginRedirect(object):
+class AjaxLoginRedirect(MiddlewareMixin):
 
     def process_response(self, request, response):
         if request.is_ajax():
@@ -23,7 +24,7 @@ class AjaxLoginRedirect(object):
         return response
 
 
-class CommonExceptionCatcher(object):
+class CommonExceptionCatcher(MiddlewareMixin):
     """Modoboa exceptions catcher."""
 
     def process_exception(self, request, exception):
@@ -44,7 +45,7 @@ class CommonExceptionCatcher(object):
         )
 
 
-class RequestCatcherMiddleware(object):
+class RequestCatcherMiddleware(MiddlewareMixin):
     """Simple middleware to store the current request."""
 
     def process_request(self, request):
diff --git a/modoboa/lib/migrations/0001_initial.py b/modoboa/lib/migrations/0001_initial.py
index 02453b798..6f5cd6f93 100644
--- a/modoboa/lib/migrations/0001_initial.py
+++ b/modoboa/lib/migrations/0001_initial.py
@@ -29,7 +29,7 @@ class Migration(migrations.Migration):
                 ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                 ('name', models.CharField(max_length=255)),
                 ('value', models.CharField(max_length=255)),
-                ('user', models.ForeignKey(to=settings.AUTH_USER_MODEL)),
+                ('user', models.ForeignKey(to=settings.AUTH_USER_MODEL, on_delete=models.CASCADE)),
             ],
             options={
             },
diff --git a/modoboa/limits/migrations/0001_initial.py b/modoboa/limits/migrations/0001_initial.py
index 468235c9b..2c1d96230 100644
--- a/modoboa/limits/migrations/0001_initial.py
+++ b/modoboa/limits/migrations/0001_initial.py
@@ -29,7 +29,7 @@ class Migration(migrations.Migration):
             name='LimitsPool',
             fields=[
                 ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
-                ('user', models.OneToOneField(to=settings.AUTH_USER_MODEL)),
+                ('user', models.OneToOneField(to=settings.AUTH_USER_MODEL, on_delete=models.CASCADE)),
             ],
             options={
                 'db_table': 'limits_limitspool',
@@ -39,7 +39,7 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name='limit',
             name='pool',
-            field=models.ForeignKey(to='limits.LimitsPool'),
+            field=models.ForeignKey(to='limits.LimitsPool', on_delete=models.CASCADE),
             preserve_default=True,
         ),
         migrations.AlterUniqueTogether(
diff --git a/modoboa/limits/migrations/0003_auto_20160413_1046.py b/modoboa/limits/migrations/0003_auto_20160413_1046.py
index 438479931..625a90568 100644
--- a/modoboa/limits/migrations/0003_auto_20160413_1046.py
+++ b/modoboa/limits/migrations/0003_auto_20160413_1046.py
@@ -58,8 +58,8 @@ class Migration(migrations.Migration):
                 ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                 ('name', models.CharField(max_length=254)),
                 ('max_value', models.IntegerField(default=-2)),
-                ('content_type', models.ForeignKey(to='contenttypes.ContentType')),
-                ('user', models.ForeignKey(to=settings.AUTH_USER_MODEL)),
+                ('content_type', models.ForeignKey(to='contenttypes.ContentType', on_delete=models.CASCADE)),
+                ('user', models.ForeignKey(to=settings.AUTH_USER_MODEL, on_delete=models.CASCADE)),
             ],
         ),
         migrations.AlterUniqueTogether(
diff --git a/modoboa/limits/migrations/0005_auto_20160415_1654.py b/modoboa/limits/migrations/0005_auto_20160415_1654.py
index ab97e7807..9b05b9f08 100644
--- a/modoboa/limits/migrations/0005_auto_20160415_1654.py
+++ b/modoboa/limits/migrations/0005_auto_20160415_1654.py
@@ -33,7 +33,7 @@ class Migration(migrations.Migration):
                 ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                 ('name', models.CharField(max_length=254)),
                 ('max_value', models.IntegerField(default=0)),
-                ('domain', models.ForeignKey(to='admin.Domain')),
+                ('domain', models.ForeignKey(to='admin.Domain', on_delete=models.CASCADE)),
             ],
             bases=(modoboa.limits.models.ObjectLimitMixin, models.Model),
         ),
diff --git a/modoboa/limits/models.py b/modoboa/limits/models.py
index 0797a7557..114a933c6 100644
--- a/modoboa/limits/models.py
+++ b/modoboa/limits/models.py
@@ -69,9 +69,10 @@ class ObjectLimitMixin(object):
 class UserObjectLimit(ObjectLimitMixin, models.Model):
     """Object level limit."""
 
-    user = models.ForeignKey(settings.AUTH_USER_MODEL)
+    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
     name = models.CharField(max_length=254)
-    content_type = models.ForeignKey("contenttypes.ContentType")
+    content_type = models.ForeignKey("contenttypes.ContentType",
+                                     on_delete=models.CASCADE)
     max_value = models.IntegerField(default=0)
 
     class Meta(object):
@@ -132,7 +133,7 @@ class UserObjectLimit(ObjectLimitMixin, models.Model):
 class DomainObjectLimit(ObjectLimitMixin, models.Model):
     """Per-domain limits on object creation."""
 
-    domain = models.ForeignKey("admin.Domain")
+    domain = models.ForeignKey("admin.Domain", on_delete=models.CASCADE)
     name = models.CharField(max_length=254)
     max_value = models.IntegerField(default=0)
 
diff --git a/modoboa/limits/tests/test_api.py b/modoboa/limits/tests/test_api.py
index ecfbe9d8f..4707c244b 100644
--- a/modoboa/limits/tests/test_api.py
+++ b/modoboa/limits/tests/test_api.py
@@ -5,7 +5,7 @@ from __future__ import unicode_literals
 
 from testfixtures import compare
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 
 from rest_framework.authtoken.models import Token
 
diff --git a/modoboa/limits/tests/test_domain_limits.py b/modoboa/limits/tests/test_domain_limits.py
index 3d9f44f99..92f6c8749 100644
--- a/modoboa/limits/tests/test_domain_limits.py
+++ b/modoboa/limits/tests/test_domain_limits.py
@@ -3,7 +3,7 @@
 
 from __future__ import unicode_literals
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 
 from modoboa.admin import factories as admin_factories
 from modoboa.admin.models import Domain
diff --git a/modoboa/limits/tests/test_import.py b/modoboa/limits/tests/test_import.py
index dc743b438..1b61fd0c5 100644
--- a/modoboa/limits/tests/test_import.py
+++ b/modoboa/limits/tests/test_import.py
@@ -3,7 +3,7 @@
 from __future__ import unicode_literals
 
 from django.core.files.base import ContentFile
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 
 from modoboa.admin import factories as admin_factories
 from modoboa.admin import models as admin_models
diff --git a/modoboa/limits/tests/test_user_limits.py b/modoboa/limits/tests/test_user_limits.py
index 2d87d0a72..39168a24b 100644
--- a/modoboa/limits/tests/test_user_limits.py
+++ b/modoboa/limits/tests/test_user_limits.py
@@ -3,7 +3,7 @@
 
 from __future__ import unicode_literals
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 
 from modoboa.admin.factories import populate_database
 from modoboa.admin.models import Alias, Domain
diff --git a/modoboa/relaydomains/migrations/0001_initial.py b/modoboa/relaydomains/migrations/0001_initial.py
index 0f6bff791..84cf66c6a 100644
--- a/modoboa/relaydomains/migrations/0001_initial.py
+++ b/modoboa/relaydomains/migrations/0001_initial.py
@@ -17,8 +17,8 @@ class Migration(migrations.Migration):
                 ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                 ('target_host', models.CharField(help_text='Remote destination of this domain', max_length=255, verbose_name='target host')),
                 ('verify_recipients', models.BooleanField(default=False, help_text='Check for valid recipients', verbose_name='verify recipients')),
-                ('dates', models.ForeignKey(to='admin.ObjectDates')),
-                ('domain', models.OneToOneField(null=True, to='admin.Domain')),
+                ('dates', models.ForeignKey(to='admin.ObjectDates', on_delete=models.CASCADE)),
+                ('domain', models.OneToOneField(null=True, to='admin.Domain', on_delete=models.CASCADE)),
             ],
             options={
                 'ordering': ['domain__name'],
@@ -40,7 +40,7 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name='relaydomain',
             name='service',
-            field=models.ForeignKey(to='relaydomains.Service'),
+            field=models.ForeignKey(to='relaydomains.Service', on_delete=models.CASCADE),
             preserve_default=True,
         ),
     ]
diff --git a/modoboa/relaydomains/tests.py b/modoboa/relaydomains/tests.py
index e071fee22..86c1e4fef 100644
--- a/modoboa/relaydomains/tests.py
+++ b/modoboa/relaydomains/tests.py
@@ -3,7 +3,7 @@
 from __future__ import unicode_literals
 
 from django.core.files.base import ContentFile
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.test import TestCase
 
 from modoboa.admin import factories as admin_factories
diff --git a/modoboa/templates/common/horizontal_select.html b/modoboa/templates/common/horizontal_select.html
new file mode 100644
index 000000000..d7145f734
--- /dev/null
+++ b/modoboa/templates/common/horizontal_select.html
@@ -0,0 +1,7 @@
+{% with id=widget.attrs.id %}<div{% if id %} id="{{ id }}"{% endif %}{% if widget.attrs.class %} class="{{ widget.attrs.class }}"{% endif %}>
+  {% for group, options, index in widget.optgroups %}
+    {% for option in options %}
+      {% include option.template_name with widget=option %}
+    {% endfor %}
+  {% endfor %}
+</div>{% endwith %}
\ No newline at end of file
diff --git a/modoboa/templates/common/horizontal_select_option.html b/modoboa/templates/common/horizontal_select_option.html
new file mode 100644
index 000000000..80f603bf9
--- /dev/null
+++ b/modoboa/templates/common/horizontal_select_option.html
@@ -0,0 +1,2 @@
+
+{% if wrap_label %}<label{% if widget.attrs.id %} for="{{ widget.attrs.id }}"{% endif %}{% if widget.attrs.id %} for="{{ widget.attrs.id }}"{% endif %} class="radio-inline">{% endif %}{% include "django/forms/widgets/input.html" %}{% if wrap_label %} {{ widget.label }}</label>{% endif %}
\ No newline at end of file
diff --git a/modoboa/transport/handlers.py b/modoboa/transport/handlers.py
index 91a581022..aae87601a 100644
--- a/modoboa/transport/handlers.py
+++ b/modoboa/transport/handlers.py
@@ -2,7 +2,7 @@
 
 from __future__ import unicode_literals
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.dispatch import receiver
 from django.utils.translation import ugettext as _
 
diff --git a/modoboa/transport/tests.py b/modoboa/transport/tests.py
index 052128fd6..5a35dd917 100644
--- a/modoboa/transport/tests.py
+++ b/modoboa/transport/tests.py
@@ -2,7 +2,7 @@
 
 import json
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 
 from modoboa.lib.tests import ModoAPITestCase, ModoTestCase
 
diff --git a/modoboa/transport/views.py b/modoboa/transport/views.py
index 944c97a9c..91298a082 100644
--- a/modoboa/transport/views.py
+++ b/modoboa/transport/views.py
@@ -1,7 +1,7 @@
 """Transport views."""
 
 from django import http
-from django.core.urlresolvers import reverse, reverse_lazy
+from django.urls import reverse, reverse_lazy
 from django.utils.translation import ugettext as _, ugettext_lazy
 from django.views import generic
 
diff --git a/test_project/test_project/settings.py b/test_project/test_project/settings.py
index c24c7f136..0cf7bdcde 100644
--- a/test_project/test_project/settings.py
+++ b/test_project/test_project/settings.py
@@ -69,7 +69,7 @@ INSTALLED_APPS += MODOBOA_APPS
 
 AUTH_USER_MODEL = 'core.User'
 
-MIDDLEWARE_CLASSES = (
+MIDDLEWARE = (
     'x_forwarded_for.middleware.XForwardedForMiddleware',
     'django.contrib.sessions.middleware.SessionMiddleware',
     'django.middleware.common.CommonMiddleware',