diff --git a/modoboa/admin/forms.py b/modoboa/admin/forms.py
index d9dbd52c5..033f5d14e 100644
--- a/modoboa/admin/forms.py
+++ b/modoboa/admin/forms.py
@@ -84,6 +84,7 @@ class DomainFormGeneral(forms.ModelForm, DynamicForm):
                         q.save()
                     old_mail_homes = dict((mb.id, mb.mail_home) for mb in d.mailbox_set.all())
             d.save()
+            Mailbox.objects.filter(domain=d, use_domain_quota=True).update(quota=d.quota)
             if old_mail_homes is not None:
                 for mb in d.mailbox_set.all():
                     mb.rename_dir(old_mail_homes[mb.id])
@@ -511,9 +512,10 @@ class AccountFormMail(forms.Form, DynamicForm):
     quota = forms.IntegerField(
         label=ugettext_lazy("Quota"),
         required=False,
-        help_text=_("Quota in MB for this mailbox. Leave empty to use the value defined at domain level."),
+        help_text=_("Quota in MB for this mailbox. Define a custom value or use domain's default one. Leave empty to define an unlimited value (not allowed for domain administrators)."),
         widget=forms.widgets.TextInput(attrs={"class": "span1"})
     )
+    quota_act = forms.BooleanField(required=False)
     aliases = forms.EmailField(
         label=ugettext_lazy("Alias(es)"),
         required=False,
@@ -534,8 +536,12 @@ class AccountFormMail(forms.Form, DynamicForm):
                 name = "aliases_%d" % cpt
                 self._create_field(forms.EmailField, name, alias.full_address)
                 cpt += 1
-            self.fields["email"].initial = self.mb.full_address
-            self.fields["quota"].initial = self.mb.quota
+            self.fields["email"].initial = self.mb.full_address            
+            self.fields["quota_act"].initial = self.mb.use_domain_quota
+            if not self.mb.use_domain_quota and self.mb.quota:
+                self.fields["quota"].initial = self.mb.quota
+        else:
+            self.fields["quota_act"].initial = True
 
         if len(args) and isinstance(args[0], QueryDict):
             self._load_from_qdict(args[0], "aliases", forms.EmailField)
@@ -557,15 +563,19 @@ class AccountFormMail(forms.Form, DynamicForm):
         if not user.can_access(domain):
             raise PermDeniedException
 
+        if self.cleaned_data["quota_act"]:
+            self.cleaned_data["quota"] = None
+
         if not hasattr(self, "mb") or self.mb is None:
             try:
                 self.mb = Mailbox.objects.get(address=locpart, domain=domain)
             except Mailbox.DoesNotExist:
                 events.raiseEvent("CanCreate", user, "mailboxes")
-                self.mb = Mailbox()
-                self.mb.save_from_user(locpart, domain, account,
-                                       self.cleaned_data["quota"],
-                                       owner=user)
+                self.mb = Mailbox(address=locpart, domain=domain, user=account,
+                                  use_domain_quota=self.cleaned_data["quota_act"])
+                self.mb.set_quota(self.cleaned_data["quota"], 
+                                  user.has_perm("admin.add_domain"))
+                self.mb.save()
                 grant_access_to_object(user, self.mb, is_owner=True)
                 events.raiseEvent("CreateMailbox", user, self.mb)
                 if user.is_superuser and not self.mb.user.has_perm("admin.add_domain"):
@@ -587,7 +597,9 @@ class AccountFormMail(forms.Form, DynamicForm):
                 self.mb.address = locpart
                 q.username = self.mb.full_address
                 q.save()
-            self.mb.set_quota(self.cleaned_data["quota"], user.has_perm("admin.add_domain"))
+            self.mb.use_domain_quota = self.cleaned_data["quota_act"]
+            override_rules = True if not self.mb.quota or user.has_perm("admin.add_domain") else False
+            self.mb.set_quota(self.cleaned_data["quota"], override_rules)
             self.mb.save()
             if old_mail_home is not None:
                 # Problem here: the mailbox has already been saved so,
diff --git a/modoboa/admin/models.py b/modoboa/admin/models.py
index 383e243d3..aee63f5a5 100644
--- a/modoboa/admin/models.py
+++ b/modoboa/admin/models.py
@@ -440,8 +440,9 @@ class User(DUser):
                 raise AdminError(_("Account import failed (%s): domain does not exist" % self.username))
             if not user.can_access(domain):
                 raise PermDeniedException
-            mb = Mailbox()
-            mb.save_from_user(mailbox, domain, self, owner=user)
+            mb = Mailbox(address=mailbox, domain=domain, user=self, use_domain_quota=True)
+            mb.set_quota(override_rules=user.has_perm("admin.change_domain"))
+            mb.save()
             self.save()
         if grpname == "DomainAdmins":
             for domname in row[8:]:
@@ -586,6 +587,7 @@ class Domain(DatesAware):
     def to_csv(self, csvwriter):
         csvwriter.writerow(["domain", self.name, self.quota, self.enabled])
 
+
 class DomainAlias(DatesAware):
     name = models.CharField(ugettext_lazy("name"), max_length=100, unique=True,
                             help_text=ugettext_lazy("The alias name"))
@@ -641,7 +643,8 @@ class Mailbox(DatesAware):
         ugettext_lazy('address'), max_length=100,
         help_text=ugettext_lazy("Mailbox address (without the @domain.tld part)")
         )
-    quota = models.IntegerField()
+    quota = models.PositiveIntegerField()
+    use_domain_quota = models.BooleanField(default=False)
     domain = models.ForeignKey(Domain)
     user = models.ForeignKey(User)
 
@@ -718,20 +721,25 @@ class Mailbox(DatesAware):
         if code:
             raise AdminError(_("Failed to remove mailbox: %s" % output))
 
-    def set_quota(self, value, override_domain=False):
+    def set_quota(self, value=None, override_rules=False):
         """Set or update quota's value for this mailbox.
 
         :param integer value: the quota's value
-        :param bool override_domain: allow to override domain's limit or not
+        :param bool override_rules: allow to override defined quota rules
         """
         if value is None:
-            self.quota = self.domain.quota
-        elif int(value) > self.domain.quota and not override_domain:
+            if self.use_domain_quota:
+                self.quota = self.domain.quota
+            else:
+                self.quota = 0
+        elif int(value) > self.domain.quota and not override_rules:
             raise AdminError(
                 _("Quota is greater than the allowed domain's limit (%dM)" % self.domain.quota)
             )
         else:
             self.quota = value
+        if not self.quota and not override_rules:
+            raise AdminError(_("A quota is required"))
 
     def get_quota(self):
         q = Quota.objects.get(username=self.full_address)
@@ -743,20 +751,9 @@ class Mailbox(DatesAware):
         q = Quota.objects.get(username=self.full_address)
         return int(q.bytes / float(self.quota * 1048576) * 100)
 
-    def save_from_user(self, localpart, domain, user, quota=None, owner=None):
-        """Simple save method called for automatic creations
-
-        :param localpart: the mailbox
-        :param domain: the associated Domain object
-        :param user: the associated User object
-        """
-        self.address = localpart
-        self.domain = domain
-        self.user = user
-        self.set_quota(quota, True if (owner and owner.has_perm("admin.add_domain")) else False)
-        super(Mailbox, self).save()
-
-        Quota.objects.create(username=self.full_address)
+    def save(self, *args, **kwargs):
+        super(Mailbox, self).save(*args, **kwargs)
+        quota, created = Quota.objects.get_or_create(username=self.full_address)
 
     def delete(self, keepdir=False):
         """Custom delete method
@@ -1030,8 +1027,9 @@ def populate_callback(user):
     try:
         mb = Mailbox.objects.get(domain=domain, address=localpart)
     except Mailbox.DoesNotExist:
-        mb = Mailbox()
-        mb.save_from_user(localpart, domain, user)
+        mb = Mailbox(address=localpart, domain=domain, user=user, use_domain_quota=True)
+        mb.set_quota()
+        mb.save()
         events.raiseEvent("CreateMailbox", sadmins[0], mb)
         grant_access_to_object(sadmins[0], mb, True)
         for su in sadmins[1:]:
diff --git a/modoboa/admin/static/admin/js/admin.js b/modoboa/admin/static/admin/js/admin.js
index b22b871d7..e8818199f 100644
--- a/modoboa/admin/static/admin/js/admin.js
+++ b/modoboa/admin/static/admin/js/admin.js
@@ -339,7 +339,7 @@ Identities.prototype = {
                 choices: get_domains_list
             })
             .dynamic_input();
-
+        activate_widget.call($("#id_quota_act"));
     },
 
     accountform_init: function() {
diff --git a/modoboa/admin/templates/admin/mailform.html b/modoboa/admin/templates/admin/mailform.html
index 01da1c26a..57655ad28 100644
--- a/modoboa/admin/templates/admin/mailform.html
+++ b/modoboa/admin/templates/admin/mailform.html
@@ -1,4 +1,4 @@
 {% load libextras %}
 {% render_field form.email %}
-{% render_field_appended form.quota _("MB") %}
+{% include "common/generic_field.html" with field=form.quota help_display_mode="tooltip" appended_text=_("MB") activator=True activator_value=form.quota_act.value deactivate_if_empty=False activator_label=_("Use domain default value") %}
 {% render_fields_group form "aliases" %}
diff --git a/modoboa/admin/tests.py b/modoboa/admin/tests.py
index a1d04f8e1..6b3a3bae9 100644
--- a/modoboa/admin/tests.py
+++ b/modoboa/admin/tests.py
@@ -77,6 +77,7 @@ class AccountTestCase(ModoTestCase):
     def test(self):
         values = dict(username="tester@test.com", first_name="Tester", last_name="Toto",
                       password1="toto", password2="toto", role="SimpleUsers",
+                      quota_act=True,
                       is_active=True, email="tester@test.com", stepid=2)
         self.check_ajax_post(reverse("modoboa.admin.views.newaccount"), values)
 
@@ -236,7 +237,7 @@ class PermissionsTestCase(ModoTestCase):
                          True)
         admin = User.objects.get(username="admin@test.com")
         values = dict(username="admin@test.com", first_name="Admin", password1="", password2="",
-                      is_active=True, email="admin@test.com")
+                      quota=10, is_active=True, email="admin@test.com")
         self.check_ajax_post(reverse("modoboa.admin.views.editaccount", args=[admin.id]), values)
         self.assertEqual(admin.group, "DomainAdmins")
         self.assertEqual(admin.can_access(Domain.objects.get(name="test.com")), True)
diff --git a/modoboa/extensions/amavis/__init__.py b/modoboa/extensions/amavis/__init__.py
index bcd96c8fd..e8e35069a 100644
--- a/modoboa/extensions/amavis/__init__.py
+++ b/modoboa/extensions/amavis/__init__.py
@@ -118,10 +118,7 @@ $(document).ready(function() {
     });
 
     $(document).bind('domform_init', function() {
-        var checked = $('#id_spam_subject_tag2_act').attr('checked');
-        if (checked && checked == 'checked') {
-            $('#id_spam_subject_tag2').attr('disabled', true);
-        }
+        activate_widget.call($('#id_spam_subject_tag2_act'));
     });
 });
 </script>""")
diff --git a/modoboa/lib/templatetags/libextras.py b/modoboa/lib/templatetags/libextras.py
index 9d8823c21..9e10c0085 100644
--- a/modoboa/lib/templatetags/libextras.py
+++ b/modoboa/lib/templatetags/libextras.py
@@ -107,9 +107,9 @@ def render_field_appended(field, text):
 @register.simple_tag
 def render_field_with_activator(field, activator_label=ugettext_lazy("activate")):
     return render_to_string("common/generic_field.html", {
-            "field" : field, "help_display_mode" : "tooltip", "activator" : True,
-            "activator_label" : activator_label
-            })
+        "field": field, "help_display_mode": "tooltip", "activator": True,
+        "activator_label": activator_label, "deactivate_if_empty": True
+    })
 
 @register.simple_tag
 def render_and_hide_field(field):
diff --git a/modoboa/templates/common/generic_field.html b/modoboa/templates/common/generic_field.html
index dd11f2af3..5c3ea7ec1 100644
--- a/modoboa/templates/common/generic_field.html
+++ b/modoboa/templates/common/generic_field.html
@@ -5,7 +5,7 @@
     {% if appended_text %}<div class="input-append">{% endif %}
     {{ field }}{% if appended_text %}<span class="add-on">{{ appended_text }}</span></div>{% endif %}{% if help_display_mode == "inline" and field.help_text %}<span class="help-inline">{{ field.help_text }}</span>{% endif %}
     {% if activator %}<label class="checkbox inline" for="id_{{ field.name }}_act">
-      <input type="checkbox" class="activator" id="id_{{ field.name }}_act" name="{{ field.name }}_act" {% if field.value == None %}checked='checked'{% endif %}/>{{ activator_label }}
+      <input type="checkbox" class="activator" id="id_{{ field.name }}_act" name="{{ field.name }}_act" {% if activator_value %}checked='checked'{% else %}{% if deactivate_if_empty and field.value == None %}checked='checked'{% endif %}{% endif %}/>{{ activator_label }}
     </label>{% endif %}
     {% if field.errors %}<p class="help-block">{% for error in field.errors %}{{ error|safe }}{% endfor %}</p>{% endif %}
   </div>