diff --git a/core/admin/mailu/internal/views/postfix.py b/core/admin/mailu/internal/views/postfix.py
index 79fbdb8a..74e49864 100644
--- a/core/admin/mailu/internal/views/postfix.py
+++ b/core/admin/mailu/internal/views/postfix.py
@@ -6,7 +6,9 @@ import flask
 
 @internal.route("/postfix/domain/<domain_name>")
 def postfix_mailbox_domain(domain_name):
-    domain = models.Domain.query.get(domain_name) or flask.abort(404)
+    domain = models.Domain.query.get(domain_name) or \
+             models.Alternative.query.get(domain_name) or \
+             flask.abort(404)
     return flask.jsonify(domain.name)