Changes

My Debian Sarge includes a GUI version called ktnef that I is bundled with KDE and integrated into KMail. Located at /usr/bin/ktnef on my system, this utility can be launched and allows you to visually open, examine the contents of, and extract the ms-tnef attachments. Since I use Mozilla for email, it doesn't know what to do with these ms-tnef attachements. So, you must first save the attachment in question before using the utility.

[1] The Mozilla project just released version 1.0 of Thunderbird, which automatically imports your Mozilla mail settings and messages, so you may want to check that out too. I assume that it is a similar process to hook up ktnef with Thunderbird.