advanced e-mail validator

check_mail.php

<?php

/**
 * Checks if the given e-mail is valid
 * Checks Done:
 * - Email has correct number of '@' and lengths
 * - Domain is valid
 * - Domain has too little parts
 * - Domain has valid parts
 * - Domain is IP
 * - Domain has a DNS MX record
 *
 * @return boolean
 */
private function checkEmailValidity($email)
{
	if (!ereg("^[^@]{1,64}@[^@]{1,255}$", $email)) return false;

	list($username, $domain) = explode("@", $email);

	if (ereg("^\[?[0-9\.]+\]?$", $domain)) return false;

	$domain_parts = explode(".", $domain);

	if (sizeof($domain_parts) < 2) return false;

	foreach ($domain_parts as $d) {

		$reg1 = "^(([A-Za-z0-9!#$%&'*+/=?^_`{|}~-][A-Za-z0-9!#$%&'*+/=?^_`{|}~\.-]{0,63})|(\"[^(\\|\")]{0,62}\"))$";

		if (!ereg($reg1, $d)) return false;

		$reg2 = "^(([A-Za-z0-9][A-Za-z0-9-]{0,61}[A-Za-z0-9])|([A-Za-z0-9]+))$";

		if (!ereg($reg2, $d)) return false;

	}

	if (!checkdnsrr($domain, 'MX')) return false;

	return true;

}

?>