I do donate to Thunderbird regularly. But I'm not happy that Mozilla put it out as a community driven project some years ago. Last I checked several months ago,

I do donate to Thunderbird regularly. But I'm not happy that Mozilla put it out as a community driven project some years ago. Last I checked several months ago, Thunderbird was going to be rewritten using web technologies. Firefox removing support for XUL extensions and moving to WebExtensions has been an issue for Thunderbird (since they share code). When Gloda (global indexing and search) arrived in Thunderbird, it was a great feature. But it's not been enhanced to make it better and to allow narrowing down on results. Emails running into tens of GBs also cause performance and responsiveness issues, probably because of the mbox format (though I haven't had corruption issues with large folders like I've heard Outlook users having once in a while). The biggest deficiency in an email client for me is the lack of proper Exchange calendaring support (no, most extensions don't cut it and have some issue or the other). I will continue donating to Thunderbird even though I've stopped using it, because it's given me many years of good experience in the past (despite some issues and deficiencies). But unless Mozilla takes it back into its fold and drives it with a larger budget, I don't foresee it coming back to the glory days of its past. Since my knowledge of the developments is at least a few months old, please correct me wherever I've said something inaccurate.