diff --git a/mo/users.py b/mo/users.py
index 2b702c70f19d63a12eb28d50bba7b6246f2331e6..98bfa52f2ecf9fc70d181d18f72a4793c41e1422 100644
--- a/mo/users.py
+++ b/mo/users.py
@@ -467,3 +467,12 @@ def request_reset_password(user: db.User, client: str) -> Optional[db.RegRequest
             details={'action': 'ask-reset'},
         )
     return rr
+
+
+def reset_user_dsn(user: db.User) -> None:
+    if user.dsn_id:
+        logger.info(f'Uživatel #{user.user_id}: Reset DSN')
+        user.dsn_id = None
+        conn = db.get_session().connection()
+        dsn_table = db.EmailDSN.__table__
+        conn.execute(dsn_table.delete().where(dsn_table.c.user_id == user.user_id))