[AngelBlue]

This is a good mod, however, it can lead to Yahoo rejecting mail from your forums if many of your users register with Yahoo email addresses.

To avoid this, disable the use of this mod on Yahoo-based email addresses, via replacing :

 if (!validate_email($vbulletin->GPC['email'])) {
   $userdata->error('os_email_notvalid');
 }

with :

if (!preg_match("/yahoo/i", $vbulletin->GPC['email'])) {
 if (!validate_email($vbulletin->GPC['email'])) {
   $userdata->error('os_email_notvalid');
 }
}

in the product file before install.
The search string is deliberately kept as "yahoo", and not "yahoo.com", to avoid cases of other possible domains (like "yahoo.fr" and "yahoomail.someotherdomain") getting past the check.