Mail Merge Requires Restart Featured
Mass Mail and Personal Mail
OpenPGP message encryption and authentication for Thunderbird and SeaMonkey.
Mail Redirect Requires Restart Featured
Allow to redirect (a.k.a. "remail") mail messages to other recipients.
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. For Thunderbird 36 and older use version 2.0.9 (see version history)