Thunderbird IMAP responded: User is authenticated but not connected

Leider hat auch diese Anleitung (Sent items reparieren) keine Besserung gebracht

Can you provide the configuration for your sent email copy?

Können Sie die Konfiguration für Ihre gesendete E-Mail-Kopie bereitstellen?

Leider hat auch diese Anleitung (Sent items reparieren) keine Besserung gebracht

While I'm glad it seems the fix is rolled out now, we're now almost 5 business days later after I've opened my support case, still no update at all. (?!)
What's the experience from others who have had cases opened with Microsoft?

Like watching floorboards warp really. Trouble is, I know logging it has to be done.

I had a reply yesterday from the first line engineer asking for details of the Thunderbird config of one of my affected users. I pointed out that it was affecting many tenants, many MUA products, appears to have hit us all at the same point in time, didn't involve users changing config, should not have required the type of fix we have all had to do, and might even have mysteriously fixed itself (can't confirm on my tenant yet). It will be interesting to see what the next update says.

I think the harsh reality is Microsoft treat the IMAP interface as if they are doing us some great big favour by providing it. They offer no SLA on availability of it that I can see, and they can always argue (and probably would!) that a failure can never be business critical because users can always log in via browser and Outlook Online. Messing up IMAP won't impact their corporate users on MS Outlook either as they won't be using the IMAP protocol. Finally, people using a third party MUA product gives Microsoft the perfect excuse to deny all knowledge and blame the MUA/user/config until the fault is actually PROVEN onto them (as is the case with IMAP subscription they broke for some users back in November and still haven't fixed over two months later).

Add this to the fact the user base for Exchange Online is probably hundreds of thousands of tenants and millions of end users across Europe alone, and this thread with a few hundred people reporting the same issue will barely register on the scale I'm afraid.

In defense of Microsoft's first line, I actually find I get a reply quickly when I raise a ticket (typically within an hour) - but if it needs to go to Product Group as these sorts of complex/indeterminate issues do, THEY don't even seem to be accountable to their own first line, let alone us. They don't seem to feel obliged to put widespread incidents onto Service Health either - yet I see some trifling issues make it onto there.