//

// if ( checkmail( $_POST['email'] ) !== True ) {

//     echo "ERROR: You have insert an invalid mail address!";

// }

//

// ***************************************************************

// This function check the syntax of an mail address and the

// DNS entry (A-Record, MX-Record) of a mail domain.

function checkmail ( $email = Null ) {

list( $user, $host ) = explode( "@", $email );

if ( !eregi ("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,})$", $email ) 

	or !checkdnsrr( $host, "MX" ) 

	or !checkdnsrr( $host, "A" ) ) {

	return False;

} else {

	return True;

}

}