Just as a matter of interest, I assume you all know that Thunderbird may be
finding a new home this year, according to Mark Surman, executive director
of the Mozilla Foundation. This probably will make little or no difference
to users, since Thunderbird has been a purely volunteer-run project for the
past 4 years, but I find the prospect interesting, since The Apache
Foundation and The Document Foundation are both under consideration.
https://marksurman.commons.ca/2016/04/25/firefox-and-thunderbird-a-fork-in-the-road/
