Thunderbird has consistently been the least bad mail client. I've tested just about every open source client and even a few proprietary ones but nothing fits my needs. A few are close but missing some show-stoppers (like the ability to pull up full threads from a single message in my inbox).

After seeing this I donated again. $100 this time. I recommend everyone else consider how important the software they use is to them. For me Thunderbird is essential and used daily so <$10 a year is a no-brainier.

Works great as an offline, local calendar too. I use it on my PC not for email but purely for its calendar.

Glad to see more attention here it was a sad day when I found Outlook as the best email client on Android. The free ones just aren't as streamlined and clean. Swipe to archive was also a must for me. Let's hope thunderbird on Android gives it a run for its money!

Thunderbird's filtering functionality is superior to Outlook's, excited to see even more improvement of the various features in the future

Never gone for me either! Also the best solution for archiving mail offline. Good community plugins. I was and remain a big fan of Thunderbird and I'm happy to hear it might make a comeback in the mainstream.

Welcome back Thunderbird. Even if you were never gone from my place.