[Antivirus]

If you turn on the feature to show the link in the body, it will show in all emails sent from the forum, but only admins with "can admin settings" permission will be able to run the ezbounce.php script.

The way the script works is it includes the link in all emails sent from the forums. The only way the link wouldn't be in your bouncing emails is if:
A) the email was not sent by the forums
B) the email was sent from your forums before the hack was installed
C) your email client isn't showing the entire header, refer to your client's documentation on displaying the full email headers.
D) another hack you have installed is conflicting with this one. Disable all other plugins/hacks and reinstall this one.

It's been successfully tested on outlook, hotmail, yahoo, eudora, smartermail, aol, by myself, I'm sure others who have installed it are using other clients as well.