Display Mail User Agent adds an image on the right side of the "expanded header view" which displays the icon of the application with which the selected mail was written.
You will see a Mozilla icon displayed in case that person which sent the mail you're currently reading used Mozilla to send this mail.
The Display Mail User Agent add-on is cross-platform and it works on Mac OS X, Windows and Linux.
· SeaMonkey 2.0 and later or
· Thunderbird 2.0 and later
What's New in This Release: [ read full changelog ]
· Added some more icons (1861 now)
· Supported mail headers: 6361 of 10298 (61.8%) with URL (60.9%)