diff --git a/orchestra/contrib/mailboxes/admin.py b/orchestra/contrib/mailboxes/admin.py
index ad405e80..f22308c7 100644
--- a/orchestra/contrib/mailboxes/admin.py
+++ b/orchestra/contrib/mailboxes/admin.py
@@ -174,6 +174,15 @@ class MailboxAdmin(ChangePasswordAdminMixin, SelectAccountAdminMixin, ExtendedMo
     
     def save_model(self, request, obj, form, change):
         """ save hacky mailbox.addresses and local domain clashing """
+        if obj.filtering != obj.CUSTOM:
+            msg = _("You have provided a custom filtering but filtering "
+                    "selected option is %s") % obj.get_filtering_display()
+            if change:
+                old = Mailbox.objects.get(pk=obj.pk)
+                if old.custom_filtering != obj.custom_filtering:
+                    messages.warning(request, msg)
+            elif obj.custom_filtering:
+                messages.warning(request, msg)
         super(MailboxAdmin, self).save_model(request, obj, form, change)
         obj.addresses = form.cleaned_data['addresses']
 
diff --git a/orchestra/contrib/mailboxes/forms.py b/orchestra/contrib/mailboxes/forms.py
index 1675af03..63c5cde3 100644
--- a/orchestra/contrib/mailboxes/forms.py
+++ b/orchestra/contrib/mailboxes/forms.py
@@ -15,8 +15,8 @@ class MailboxForm(forms.ModelForm):
     """ hacky form for adding reverse M2M form field for Mailbox.addresses """
     # TODO keep track of this ticket for future reimplementation
     #      https://code.djangoproject.com/ticket/897
-    addresses = forms.ModelMultipleChoiceField(queryset=Address.objects.select_related('domain'),
-        required=False,
+    addresses = forms.ModelMultipleChoiceField(required=False,
+        queryset=Address.objects.select_related('domain'),
         widget=widgets.FilteredSelectMultiple(verbose_name=_('addresses'), is_stacked=False))
     
     def __init__(self, *args, **kwargs):
@@ -30,16 +30,17 @@ class MailboxForm(forms.ModelForm):
         self.fields['addresses'].widget = widgets.RelatedFieldWidgetWrapper(widget, field,
                 self.modeladmin.admin_site, can_add_related=True)
         
+        account = self.modeladmin.account
         # Filter related addresses by account
         old_render = self.fields['addresses'].widget.render
         def render(*args, **kwargs):
             output = old_render(*args, **kwargs)
-            args = 'account=%i' % self.modeladmin.account.pk
+            args = 'account=%i' % account.pk
             output = output.replace('/add/?', '/add/?%s&' % args)
             return mark_safe(output)
         self.fields['addresses'].widget.render = render
         queryset = self.fields['addresses'].queryset
-        realted_addresses = queryset.filter(account_id=self.modeladmin.account.pk).order_by('name')
+        realted_addresses = queryset.filter(account_id=account.pk).order_by('name')
         self.fields['addresses'].queryset = realted_addresses
         
         if self.instance and self.instance.pk:
diff --git a/orchestra/contrib/mailboxes/models.py b/orchestra/contrib/mailboxes/models.py
index aae48ef4..cb0630de 100644
--- a/orchestra/contrib/mailboxes/models.py
+++ b/orchestra/contrib/mailboxes/models.py
@@ -60,9 +60,7 @@ class Mailbox(models.Model):
         return os.path.normpath(settings.MAILBOXES_HOME % context)
     
     def clean(self):
-        if self.custom_filtering and self.filtering != self.CUSTOM:
-            self.custom_filtering = ''
-        elif self.filtering == self.CUSTOM and not self.custom_filtering:
+        if self.filtering == self.CUSTOM and not self.custom_filtering:
             raise ValidationError({
                 'custom_filtering': _("Custom filtering is selected but not provided.")
             })
@@ -70,6 +68,7 @@ class Mailbox(models.Model):
     def get_filtering(self):
         name, content = settings.MAILBOXES_MAILBOX_FILTERINGS[self.filtering]
         if callable(content):
+            # Custom filtering
             content = content(self)
         return (name, content)