DO NOT donate to Thunderbird. Let it "die". As with all of Mozilla's software, that would be the best outcome - if it does, someone who isn't totally incompetent might fork it and actually improve it.

Literally every change that's been made to thunderbird in the last 10+ years has made it worse. Mozilla are doggedly using the same philosophy as they are with firefox: "in what new and exciting ways can we make it more shit?".

There are a bunch of things that I used to do in thunderbird with no problem on much less powerful machines that I can't do today.

For example, since they decided to rewrite their perfectly-functional calendar parsing in a trash language, it now eats 100% of my CPU for ~30mins at a time trying to parse my decades-long, many-many-thousands-of-entries calendar. Then when it finishes it notices that it's been 30 mins since it synchronised my calendar, so it syncs and starts parsing all over again! This effectively locks up the whole of thunderbird, making it totally unusable. This issue has persisted for years. The solution I came up with is "stop using thunderbird for my calendar".

There's a similar fun bug which means it won't sync my contacts anymore either. A feature that I had by about 2010 which my nokia phone could manage, modern thunderbird cannot do.

If you'd like another 20 examples of how it's worse today than it was 10 years ago, just ask, and I'll write up a hundred thousand words or so of vitriol.

It's extremely likely that next time I upgrade my distro I'll be shopping for a new email client. Currently I have thunderbird marked as held so that it doesn't upgrade. When I upgrade my distro there will be a new version of thunderbird, and I'd estimate about a 90% chance that that's when I'll make my exit, after ~20 years or so.

It's sad. Thunderbird used to be a great piece of software.

Don't give mozilla your money.