diff --git a/modoboa/admin/forms/account.py b/modoboa/admin/forms/account.py
index d08d3fff4..8fd2572b6 100644
--- a/modoboa/admin/forms/account.py
+++ b/modoboa/admin/forms/account.py
@@ -403,6 +403,7 @@ class AccountFormMail(forms.Form, DynamicForm):
 
     def _update_aliases(self, user, account):
         """Update mailbox aliases."""
+        # 1. We check if existing aliases were removed...
         qset = self.mb.aliasrecipient_set.select_related("alias").filter(
             alias__internal=False)
         for ralias in qset:
@@ -414,22 +415,26 @@ class AccountFormMail(forms.Form, DynamicForm):
                 alias.delete()
             else:
                 self.aliases.remove(ralias.alias.address)
+        # 2. Nothing left to do, return
         if not self.aliases:
             return
+        # 3. Check limits at all levels
         core_signals.can_create_object.send(
             self.__class__, context=user, klass=models.Alias,
             count=len(self.aliases))
         core_signals.can_create_object.send(
             self.__class__, context=self.mb.domain,
             object_type="mailbox_aliases", count=len(self.aliases))
+        # 4. Create / update aliases
         for alias in self.aliases:
             if self.mb.aliasrecipient_set.select_related("alias").filter(
-                    alias__address=alias).exists():
+                    alias__address=alias, alias__internal=False).exists():
                 continue
             local_part, domname = split_mailbox(alias)
             al, _ = models.Alias.objects.get_or_create(
                 address=alias,
                 domain=models.Domain.objects.get(name=domname),
+                internal=False,
                 defaults={'enabled': account.is_active},
             )
             al.add_recipients([self.mb.full_address])
diff --git a/modoboa/admin/tests/test_account.py b/modoboa/admin/tests/test_account.py
index d47faf17e..6f1c7ab88 100644
--- a/modoboa/admin/tests/test_account.py
+++ b/modoboa/admin/tests/test_account.py
@@ -135,6 +135,26 @@ class AccountTestCase(ModoTestCase):
         self.ajax_post(reverse("admin:account_add"), values)
         self.assertTrue(alias.aliasrecipient_set.count() == 2)
 
+    def test_create_alias_on_existing_account(self):
+        values = {
+            "email": "tester@test.com",
+            "username": "tester@test.com",
+            "role": "SimpleUsers",
+            "random_password": "on",
+            "quota_act": True,
+            "is_active": True,
+            "stepid": "step2",
+            "aliases": "user@test.com",
+        }
+        self.ajax_post(reverse("admin:account_add"), values)
+        # Check that internal alias has not been updated
+        alias = models.Alias.objects.get(
+            address="user@test.com", internal=True)
+        self.assertTrue(alias.aliasrecipient_set.count() == 1)
+        alias = models.Alias.objects.get(
+            address="user@test.com", internal=False)
+        self.assertTrue(alias.aliasrecipient_set.count() == 1)
+
     def test_create_disabled_account(self):
         """Check if account and alias are disabled."""
         values = {