This mod was posted in the mod section quite some time ago and is used in the CPanel Password change mod as well. What they do is replace
// try to log in
if ($_action=='login' && $_task=='mail')
{
$host = rcmail_autoselect_host();
With this
// try to log in
if(isset($_POST['_user']) && $_action == 'login' && $_task == 'mail')
{
if($_SERVER['SERVER_NAME'] and !preg_match('/(.*)\@(.*)/',$_POST['_user'])){
$domain = preg_replace('/^(\w*)\./','',$_SERVER['SERVER_NAME']);
$_POST['_user'] = $_POST['_user']."@".$domain;
}
What that will do is allow the user to log in with just their user name and it will populate the @domain.com part with the domain name they are accessing. Rather than have my users chose from a list of domains which also shows them how many and what domains I host I prefer this method.