alt Hacker NewsI use Thunderbird from the beginning when it was still named Firebird (I switched from Outlook Express). I think that it's a good product because it continues to do the job since more than 20 years. Me too I don't understand the negative comments. It's free (MPL license), it's packaged by Debian. All good. I don't care about Mozilla.
I just check something because my memory as faults... Firebird was the name of Firefox and the mail client was called something like Mozilla mail or something else.