New in Thunderbird 78

Yes! I get so frustrated by those for that reason.

copy / paste works fine

Thanks for the recommendation, I just tried it and it seems perfect!

Contrary to your experience, I was even able to create events from thunderbird that would show up on O365. They only show up on sync however (which does not seems to be automatic, only on timer). Maybe that's the reason why it did not appear to work for you?

I've been a long time Evolution user (decades, literally). But the bugs; particularly in the mail composer. So many bugs. And a lot of dependence on how Gnome does things, like online accounts. I swear some Gnome libraries have a lifetime of split milk, and when they change everything breaks. So now I've moved to Thunderbird.

I've already come across a fair few bugs in Thunderbird. And as you say sync'ing calendars with Google is one of them. Only being able the use Google Calendar with the GMail account sharing the same email address is a complete PITA, making it unsuitable for many applications. Thunderbirds dependence on Firefox, and the current rapid internal refactoring Firefox is undergoing combine to break things even faster than Gnome. So, bug and stability wise they seem to be on par. (Lord, how I look forward to Firefox/Mozilla getting past this period. I realise it's necessary, they are doing their best to reduce the pain and what pain remains must simply be endured. But enduring it is hard.)

Feature wise, both Evolution and Thunderbird both are very mature and equally capable. Many of the deficiencies in both arise from the proprietary providers (Google, Microsoft, ...) continually changing how they do things, and in Microsoft's case gratuitously making interoperability difficult.

As for the Windows Outlook client - pfft. I was asked to help a work colleague a month or two ago. During the move of data from the old machine to the new one some part of Windows (perhaps Defender?) announced a file contained copyrighted material and deleted it. The file happened to be the .PST containing his pop3 data. After getting past that a week or two later it refused to start. It announced Windows was running low on resources, then exited. I last saw that message 25 years ago, when Outlook was the only choice. The only solution was a complete uninstall (which of course Microsoft's installer doesn't know how to do, so it must be done manually, stumbling around in the dark), and clean install. Nothing has changed.

Whereas the open source clients do their best to interoperate with everything (albeit with mixed success), Microsoft appears to go out of their way to make their users' lives difficult if they try to use Outlook with anything bar Microsoft servers (online or Exchange). The corporate world would be far better off collectively getting behind someone like RedHat, Ubuntu or the Apache foundation, and developing something whose primary goal was to do the job they need done well, not extract money from them. It’s not like it’s a mind boggling difficult job.

Try adding the root CA cert you created to sign the self-signed cert to whatever certificate trust store Thunderbird uses on your system, maybe? It's been a while since I had to deal with this on any OS so I can't give specific advice on how to do it, but generally my experience has been that this is a good first step in resolving trust failures with self-signed certificates.

Thanks! Now looks like need to upgrade my TLS!

Happy to hear.

I'm just a mere mortal though.

After following your instructions, I did not notice an improvement in performance.

Cool, but at that point I would probably just stick with what I have until it can be natively supported, or see if their current config is easy to template myself.