diff --git a/core/admin/mailu/internal/views/postfix.py b/core/admin/mailu/internal/views/postfix.py
index d1b53856..7c3c9cdb 100644
--- a/core/admin/mailu/internal/views/postfix.py
+++ b/core/admin/mailu/internal/views/postfix.py
@@ -133,11 +133,10 @@ def postfix_sender_map(sender):
 
 @internal.route("/postfix/sender/login/<path:sender>")
 def postfix_sender_login(sender):
-    has_wildcard_senders = bool(flask.current_app.config["WILDCARD_SENDERS"])
-    wildcard_senders = flask.current_app.config["WILDCARD_SENDERS"].lower().split(',') if has_wildcard_senders else []
+    wildcard_senders = [s for s in config.get('WILDCARD_SENDERS', '').lower().replace(' ', '').split(',') if s]
     localpart, domain_name = models.Email.resolve_domain(sender)
     if localpart is None:
-        return flask.jsonify(",".join(wildcard_senders)) if has_wildcard_senders else flask.abort(404)
+        return flask.jsonify(",".join(wildcard_senders)) if wildcard_senders else flask.abort(404)
     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)