use RECIPIENT_DELIMITER for splitting

core/admin/mailu/configuration.py

@@ -49,6 +49,7 @@ DEFAULT_CONFIG = {
     'DKIM_PATH': '/dkim/{domain}.{selector}.key',
     'DEFAULT_QUOTA': 1000000000,
     'MESSAGE_RATELIMIT': '200/day',
+    'RECIPIENT_DELIMITER': None,
     # Web settings
     'SITENAME': 'Mailu',
     'WEBSITE': 'https://mailu.io',

core/admin/mailu/internal/views/postfix.py

@@ -140,8 +140,9 @@ 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)
-    user, plus = localpart.split("+", 1)
+    if delim := flask.current_app.config.get('RECIPIENT_DELIMITER'):
-    destination = models.Email.resolve_destination(user, domain_name, True)
+        localpart = localpart.split(delim, 1)[0]
+    destination = models.Email.resolve_destination(localpart, domain_name, True)
     destination = [*destination, *wildcard_senders] if destination else [*wildcard_senders]
     return flask.jsonify(",".join(destination)) if destination else flask.abort(404)