$re = '/^([a-zA-Z0-9_\-\\\\.]+)@((\\\\[[0-9]{1,3}\\\\.[0-9]{1,3}\\\\.[0-9]{1,3}\\\\.)|(([a-zA-Z0-9\\\\-]+\\\\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\\\\]?)$/m';
$str = 'hitesh-bedre@\\XX\\XX\\XX\\XXX\\
hitesh-bedre@XX\\XXX\\
';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php