$re = '/^(?:2018|201[0-7]|200[0-9]|1[0-9]{1,3}|[0-9]{1,3})\.[a-zA-Z]\.[a-zA-Z]@\w+(?:\.\w+)*\.com\.co$/m';
$str = '0.j.g@cloudmail.com.co
50.j.g@cloudmail.com.co
444.j.g@cloudmail.com.co
999.j.g@cloudmail.com.co
2018.j.g@cloudmail.com.co
2019.j.g@cloudmail.com.co
2020.j.g@cloudmail.com.co';
preg_match_all($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