Yeap. It's mentioned in their financial reports that user donations represent more than 99.9% of our annual revenue[0]. Also seems their staff is mainly engineers/developers, and all the expenses are concentrated to their product*. Thunderbird doing what Firefox should.
As of right now Thunderbird doesn't make any money, it relies on 'Donations' which isn't at all sustainable.
I can see Thunderbird is planning to do a pro plan, but it is behind a waitlist so the total sum of revenue Thunderbird is making relative to Google's $500M deal is close to zero.
