diff --git a/core/admin/mailu/internal/nginx.py b/core/admin/mailu/internal/nginx.py
index b7e246af..2ee6d9b3 100644
--- a/core/admin/mailu/internal/nginx.py
+++ b/core/admin/mailu/internal/nginx.py
@@ -94,11 +94,11 @@ def handle_authentication(headers):
         else:
             try:
                 user = models.User.query.get(user_email) if '@' in user_email else None
-                is_valid_user = user is not None
             except sqlalchemy.exc.StatementError as exc:
                 exc = str(exc).split('\n', 1)[0]
                 app.logger.warn(f'Invalid user {user_email!r}: {exc}')
             else:
+                is_valid_user = user is not None
                 ip = urllib.parse.unquote(headers["Client-Ip"])
                 if check_credentials(user, password, ip, protocol, headers["Auth-Port"]):
                     server, port = get_server(headers["Auth-Protocol"], True)