Mozilla is going to stop doing even light development on Thunderbird, the desktop email client. It’s a shame that they’re doing this but understandable as Firefox has been losing market share to Chrome and even Microsoft is open sourcing their web browser rendering engine.
Thunderbird has always been a reliable email client, always just working and even making it easy to use webmail servers like Yahoo or GMail. I highly recommend that people use it.
My guess is that some developers who really like Thunderbird will hop in and keep developing it. Perhaps we’ll see a repeat of the LibreOffice/OpenOffice situation where the pace of development and bug fixes becomes very rapid.
It would be cool to see Thunderbird used as a place for experimentation too, perhaps being the one stop shop for handling notifications from other services like Slack or JIRA.