Merge pull request roundcube#9668 from idressos/virtuser_file-email2u…

…ser-fix

Fix virtuser_file plugin email2user() function not accounting for backward slashes in username

plugins/virtuser_file/virtuser_file.php

@@ -68,7 +68,9 @@ public function email2user($p)
             $arr = preg_split('/\s+/', trim($r[$i]));
 
             if (count($arr) > 0) {
-                $p['user'] = trim($arr[count($arr) - 1]);
+                // Replace '\@' with '@' to handle cases where internal usernames include an '@' character.
+                // Sometimes usernames with '@' are saved with a leading '\' to avoid conflicts.
+                $p['user'] = trim(str_replace('\@', '@', $arr[count($arr) - 1]));
                 break;
             }
         }