Mail says Attachment Tamer is incompatible.
It may happen that Mail disables the plug-in and displays a window with a message saying Incompatible Plug-ins Disabled (or a Bundle Compatibility Warning). According to Apple “Mail plugins are automatically disabled” after some Mac OS X updates because “does not support the installation or use of third-party plugins with Mail.app”.
If this happens, check for a new release of Attachment Tamer compatible with your version of Mac OS X (and thus also the Message and Mail software released with it), download it and reinstall. You do not need to worry that your settings or registration will be lost if the plug-in is disabled and then reinstalled.
If you want to prevent compatibility problems, either enable automated update checking and keep your installation up-to-date, or check check for a new release on the web before installing a Mac OS X update.
You may also receive a warning saying that Attachment Tamer could not load, which is a different problem.