I got if worked out, just hacked at the users.php and english.php files. Here's what I came up with is working just fine:
In users.php, directly below
case 'create':Text Formatted Code
// Adding code to try an block cashette.com registrations.
if ((isset($_POST['email'])) && (eregi("cashette.com", $_POST['email']))) {
$display .= COM_siteHeader ('menu');
$display .= COM_startBlock ($LANG04[21], '',
COM_getBlockTemplate ('_msg_block', 'header'))
. $LANG04[124]
. COM_endBlock (COM_getBlockTemplate ('_msg_block', 'footer'));
$display .= COM_siteFooter ();
COM_accesslog("BANCONTROL: Denied registration for blocked domain -- ".$_POST['email']." ");
break;
}
and in languages english.php in the LANG04 array:
Text Formatted Code
124 => "<img src='/images/arrow.gif?'> Registration cancelled. Email address domain cashette.com is not allowed here. <a href="{$_CONF['site_url']}/users.php?mode=new">Click Here</a> to register with a different email address."
Maybe this will help someone looking to do similar.
Edited to add logging as well.