Try...
<?PHP
$query = mysql_query( "SELECT email FROM mailinglist" );
while( $myrow = mysql_fetch_assoc( $query ) )
{
echo mail( $myrow['email'], 'Subject', 'Message' ) ? 'Message sent to ' . $myrow['email'] : 'Message NOT sent to ' . $myrow['email'];
echo '<br>';
}
?>