diff --git a/core/admin/mailu/internal/views/postfix.py b/core/admin/mailu/internal/views/postfix.py
index 928f4faf..d2c9f877 100644
--- a/core/admin/mailu/internal/views/postfix.py
+++ b/core/admin/mailu/internal/views/postfix.py
@@ -140,7 +140,8 @@ def postfix_sender_login(sender):
     localpart, domain_name = models.Email.resolve_domain(sender)
     if localpart is None:
         return flask.jsonify(",".join(wildcard_senders)) if wildcard_senders else flask.abort(404)
-    destination = models.Email.resolve_destination(localpart, domain_name, True)
+    user, plus = localpart.split("+", 1)
+    destination = models.Email.resolve_destination(user, domain_name, True)
     destination = [*destination, *wildcard_senders] if destination else [*wildcard_senders]
     return flask.jsonify(",".join(destination)) if destination else flask.abort(404)