$re = '/^[\p{L}\d!#$%&\'*+/=?^_`{|}~-]+(?:\.[\p{L}\d!#$%&\'*+/=?^_`{|}~-]+)*@[\p{L}\d]+(?:[.-][\p{L}\d]+)*\.\p{L}{2,}$/um';
$str = 'test.user@example.com
test-user@ex-ample.com
test.user+123@example.com
dörte@sörensen.example.com
χρήστης@παράδειγμα.ελ
иван@поща.бг
خالد@الدوحة.قط
שלום@דוגמה.ישראל';
preg_match_all($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