$re = '/^[a-zA-Z]\.[a-zA-Z]\.(?:2019|20[2-9][0-9]|2[1-9][0-9]{2}|[3-9][0-9]{3})@uts\.edu\.co$/m';
$str = 'j.g.1999@uts.edu.co
j.g.2018@uts.edu.co
j.g.2019@uts.edu.co
j.g.2020@uts.edu.co
j.g.2099@uts.edu.co
j.g.2119@uts.edu.co
j.g.4904@uts.edu.co';
preg_match_all($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