function check_email_address($email) {
 // First, we check that there's one @ symbol, and that the lengths are right
 if (!ereg("^[^@]{1,64}@[^@]{1,255}$", $email)) {
 // Email invalid because wrong number of characters in one section, or wrong number of @ symbols.
 return false;
 }
 // Split it into sections to make life easier
 $email_array = explode("@", $email);
 $local_array = explode(".", $email_array[0]);
 for ($i = 0; $i < sizeof($local_array); $i++) {
 if (!ereg("^(([A-Za-z0-9!#$%&'*+/=?^_`{|}~-][A-Za-z0-9!#$%&'*+/=?^_`{|}~\.-]{0,63})|(\"[^(\\|\")]{0,62}\"))$", $local_array[$i])) {
 return false;
 }
 }
 if (!ereg("^\[?[0-9\.]+\]?$", $email_array[1])) { // Check if domain is IP. If not, it should be valid domain name
 $domain_array = explode(".", $email_array[1]);
 if (sizeof($domain_array) < 2) {
 return false; // Not enough parts to domain
 }
 for ($i = 0; $i < sizeof($domain_array); $i++) {
 if (!ereg("^(([A-Za-z0-9][A-Za-z0-9-]{0,61}[A-Za-z0-9])|([A-Za-z0-9]+))$", $domain_array[$i])) {
 return false;
 }
 }
 }
 return true;
 }