Thunderbird seems to run everything in a single thread, something I only noticed when I tried to sync some large mailing list folders and the UI basically became unusable. I was really hoping to switch to it before this cropped up.

I've paid for and been a happy user of https://www.beonex.com/owl/ when I've needed to in the past.

Outlook has been falling apart at the seams for a while now. But I cannot find a email client that supports multiple exchange servers and parses calendar invites in a way that's compatible with Teams. I'm the first to jeet Outlook if Thunderbird will do this but I'm also open to suggestions here.

It is a losing proposition to try to deal with compatibility between different MS products. Especially moving SaaS targets you can't control.

I just this week lost access to my hotmail/outlook account from Thunderbird, although I'm on a much older version. Sounds like MS dropped POP3 support, probably for my own 'safety and security'. How long has that been an industry standard though, shame. Anyway a good trigger to drop another ad focused company, at least that is what it seems when I was forced to use the web interface today.

> probably for my own 'safety and security'

Yes, your safety and security from Microsoft.

Thunderbird will support EWS, which if you use a cloud based Exchange account will be unavailable in 2026.