"mozilla mail" developer resources have waxed and waned over the years, and the most recent announcement that Mozilla are no longer supporting thunderbird development, reminded me that the usage of Mozilla email clients has been the most constant technology thread that I've used in my 20 year tech career to date.

[Update Dec 2017: Mozilla have announced a few new staff have been hired to maintain the project.]

Now I try not to get inappropriately attached to any technology, though I've not noticed any email client significantly better to warrant a switch. It's interesting to see the general move from local clients to hosted email like gmail which currently has about 1 billion users (compared to thunderbird's 10 million), though personally I've found the control and flexibility of having all my mail locally, very useful.

It'll be interesting to see how messaging evolves, given the recent increase in divergence rate from email to irc, slack, whatsapp, facebook, ... Here is a recent summary of innovation in the email space.

1995 - Netscape navigator 2 mail

My first experience with Netscape email was with the navigator 2 client, which I switched to after having stability issues with Eudora.
netscape navigator 2 email client

1997 - Netscape communicator 4 mail

This was quite an improvement in functionality and interface.
netscape communicator email client

1998 - Pegasus Mail 3

This is not a Mozilla email client, but I'm adding it here for completeness, as I used it for a few months. I'm still able to run this in 2021 under wine, but note it doesn't run under the default wine configuration, which gives the error "The user you are attempting to 'become' does not exist on this system". Instead one needs to instruct wine to provide support for older windows variants (like windows 95), like:
WINEARCH=win32 WINEPREFIX=$HOME/.wine32 winemine  # init the prefix dir
mv PMAIL/ ~/.wine32/drive_c/  # Needs to run from this hierarchy
  wine ~/.wine32/drive_c/PMAIL/winpm-32.exe -a -i padraigb
pegasus windows email client

1999 - Mozilla mail and newsgroups

I used this separated version (generally with the pinball theme) for a few years after the open sourcing of netscape to Mozilla.
mozilla mail and newsgroups

2005 - Thunderbird 1

The first thunderbird version I used, and I also stopped using news groups around this time but transitioned to reading blog feeds from within thunderbird.
thunderbird 1

2010 - Thunderbird 3

This was the last major update really to thunderbird, which I reviewed separately at the time, and had a new vertical layout.
thunderbird 3 vertical layout

2015 - Thunderbird 38

Not significantly different to warrant a screenshot. It'll be interesting to see where the community takes it from here.

[Update May 2017: Thunderbird is to separate from mozilla, for technical and operational aspects at least. There have been plans mooted for a fairly major rewrite with the ousting of XUL tech in favor of newer web technologies.

2019 - Thunderbird 70

Interface stalls are now gone completely.
Dark mode styling is picked up automatically from the system.
thunderbird 3 vertical layout
© Dec 4 2015