Addon for Mozilla Thunderbird and SeaMonkey providing OpenPGP-based encryption and authentication.
Enigmail requires GnuPG.
- OpenPGP encryption
The "dropdown box" way of enabling/disabling encryption or signing is a bit annoying to use, but aside from that UI annoyance, otherwise, it does the job well. Currently annoyed by a bug that prevents `Bcc:` recipients, but that is hopefully temporary and has supposedly been fixed in the next release.