$re = ';^[a-z0-9!#$%&\'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&\'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.){1,3}[a-z0-9](?:[a-z0-9-]*[a-z0-9])?$;m';
$str = 'wiliam@hotmail.com
wiliam.ferraciolli@hotmail.com
wiliam@hotmail.co.uk
wiliam.ferraciolli@hotmail.co.uk
wiliam_ferraciolli@hotmail.co.uk
wiliam\'ferraciolli@hotmail.co.uk
wiliam334-1@mydomain.co.uk.me
wiliam.ferraciolli@hotmail.com.dodge.too.many
hwiliam@hotmail.com.otherdomain.uk.dodge
wiliam.ferraciolli@hotmail.com.com.com.com
wiliam.hotmail.com
wiliam..ferraciolli@hotmail.com
wiliam%ferraciolli.@hotmail.com
wiliam$ferraciolli.@hotmail.com
wiliam/ferraciolli.@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