$re = '/\A(?=[a-z0-9@.!#$%&\'*+\/=?^_`{|}~-]{6,254}\z)
(?=[a-z0-9.!#$%&\'*+\/=?^_`{|}~-]{1,64}@)
[a-z0-9!#$%&\'*+\/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&\'*+\/=?^_`{|}~-]+)*
@ (?:(?=[a-z0-9-]{1,63}\.)[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+
(?=[a-z0-9-]{1,63}\z)[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\z/m';
$str = 'ragedog@hotmail.com';
preg_match_all($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