diff --git a/modoboa/extensions/admin/forms/account.py b/modoboa/extensions/admin/forms/account.py
index 1b3ef6b10..3d929f697 100644
--- a/modoboa/extensions/admin/forms/account.py
+++ b/modoboa/extensions/admin/forms/account.py
@@ -272,7 +272,7 @@ class AccountFormMail(forms.Form, DynamicForm):
                 continue
             if value == "":
                 continue
-            aliases.append(value)
+            aliases.append(value.lower())
 
         for alias in self.mb.alias_set.all():
             if alias.full_address not in aliases:
diff --git a/modoboa/extensions/admin/forms/alias.py b/modoboa/extensions/admin/forms/alias.py
index 1a999fe49..12485eebc 100644
--- a/modoboa/extensions/admin/forms/alias.py
+++ b/modoboa/extensions/admin/forms/alias.py
@@ -82,7 +82,7 @@ class AliasForm(forms.ModelForm, DynamicForm):
             raise forms.ValidationError(
                 _("You don't have access to this domain")
             )
-        return self.cleaned_data["email"]
+        return self.cleaned_data["email"].lower()
 
     def set_recipients(self):
         """Recipients dispatching