diff --git a/core/admin/mailu/internal/nginx.py b/core/admin/mailu/internal/nginx.py
index 7613c48a..4df8f55a 100644
--- a/core/admin/mailu/internal/nginx.py
+++ b/core/admin/mailu/internal/nginx.py
@@ -77,7 +77,7 @@ def handle_authentication(headers):
     # Authenticated user
     elif method == "plain":
         is_valid_user = False
-        if 'Auth-Port' in headers and int(urllib.parse.unquote(headers["Auth-Port"])) == 25:
+        if headers["Auth-Port"] == '25':
             return {
                 "Auth-Status": "AUTH not supported",
                 "Auth-Error-Code": "502 5.5.1",