[ilyt]

Probably talking about

https://addons.thunderbird.net/en-US/thunderbird/addon/owl-f...

which is paid.

Can achieve feature parity with plain IMAP + TbSync but that's another 3rd party addon.

So "doesn't work out of the box with o365" isn't that big of a stretch, plain TB will only get you IMAP working.

That's honestly more of MS being cancer and not using standards than anything else.

They also introduced required OAUTH2 authentication last year and in a way that you need essentially org admin rights to give any other client than TB access... because you need to create fucking app in MS panels that then gets used by mail client to authorize you. It is entirely aisine platform