The Thunderbird developers have announced that they will implement OpenPGP support in Thunderbird 78. Support for Thunderbird in Enigmail will therefore be discontinued.
We would like to explain in the following paragraphs what this will mean for Enigmail, and why this is an inevitable step.
The Future of Enigmail
We will continue to support and maintain Enigmail for Thunderbird 68 until 6 months after Thunderbird 78 will have been released (i.e. a few months beyond Thunderbird 68 EOL). Enigmail will not run anymore on Thunderbird 72 beta and newer.
Will this be the end of Enigmail?
No! We will continue to maintain and support Enigmail for Postbox, which is running on a different release schedule than Thunderbird for the foreseeable future.
Why Is This Happening?
The Mozilla developers have been and still are actively working on removing old code from their code base. This affects not only Thunderbird itself, but also add-ons. While it was possible for Thunderbird to keep old "legacy" add-ons alive for a certain time, the time has come for Thunderbird to stop supporting them. Thunderbird 78 will no longer to support the APIs that Enigmail requires and only allow new "WebExtensions".
WebExtensions have a completely different API than classical add-ons, and a much reduced set of capabilities to hook into the user interface. For Enigmail to continue to work, it would therefore be required to rewrite it from scratch. However, that's beyond my available time limitations.
We have therefore agreed with the Thunderbird developers that it's much better to implement OpenPGP support directly in Thunderbird. The set of functionalities will be different than what Enigmail offers, and at least initially likely be less feature-rich. But in our eyes, this is by far outweighed by the fact that OpenPGP will be part of Thunderbird and no add-on and no third-party tool will be required.