[PHP]
<?php
function CheckEmailer( $mail ) 
{
	if ( eregi( '^[a-zA-Z0-9_]+@[a-zA-Z0-9\-]+\.[a-zA-Z0-9\-\.]+$]', $mail ) ) {
		return false;
	}
	list( $Username, $Domain ) = explode( '@', $mail );
	if ( getmxrr( $Domain, $MXHost ) ) {
		return true;
	} else {
		return false;
	} 

} 
?>