Mail Merge Requires Restart Featured
Mass Mail and Personal Mail
CardBook Requires Restart Featured
OpenPGP message encryption and authentication for Thunderbird and SeaMonkey.
CompactHeader Requires Restart Featured
Add symbol in header plane to switch between compact and expanded view. Options to switch between one or two lines compact view, which buttons should be displayed in header pane. New beta version available from http://compactheader.mozdev.org/
Mail Redirect Requires Restart Featured
Allow to redirect (a.k.a. "remail") mail messages to other recipients.