Unable to subscribe to Office 365 IMAP folders from MUA since 2022-11-01

(the following paragraph is pure speculation from a user lacking the understanding of the actual communication protocol)

Here a wild guess out of the blue: Perhaps we are running into path length issue? I recall the property of the Windows API to limit the MAX_PATH variable to 260 characters.

Allow me to speculate: I assume that communication between user agent and server(s) depends on some kind of authentication token. It should also contain an (encrypted) account address or ID. Perhaps the list of subscribed IMAP folders is appended to account ID (or user email address) and token, and subsequently sent as part of the string in whatever server/client handshake. In this hypothetical setup, evaluation of the string on the server side may hit the size limit in some cases. This would occur in particular in cases where account names were too long?

(back to the facts)

I noticed that Ian's last email address is rather long. The name and password of my affected account are also on the longer end of the spectrum. Is there evidence suggesting a correlation between email-address, or password-length, and account behaviour?

On the length of account names, nothing I have noticed. I have a mix of affected and unaffected accounts with similar length, and one affected account that is just four characters.

The way the test script works, is that handles the Oauth2 authentication at the start of the script - and after that, the connection is open/authenticated and it is just sending a series of IMAP commands interactively with the server.

If you look below, this is the Microsoft script running against one of my affected accounts - but in this case, I commented out the last line which does a CLOSE on the IMAP session, and that leaves the session open for me to send my own commands to the server. The two commands with the green arrows are ones I have just shoved in and you can see the LSUB command fails as it did in the script.

So I don't think this is going to be related to authentication.

Thanks for keeping this going. I just got off a call with my support team and they are still thinking it is something on the client. I have to get my affected users to login on different hosts and reproduce the problem. I asked if LSUB is still the supported way to get subscribed folders and they will ask. They are not convinced it is something on the server yet.

-Jonathan

I really doubt that it is the client side:

The issue persists for me on two different systems, on one I even tried a fresh install of Thunderbird.

Assuming it were the client, then why am I not seeing these issues with my other 4 IMAP accounts on same MUA?

(The functional ones are not Microsoft O365 accounts - of course.)

I really doubt that it is the client side:

The issue persists for me on two different systems, on one I even tried a fresh install of Thunderbird.

Assuming it were the client, then why am I not seeing these issues with my other 4 IMAP accounts on same MUA?

(The functional ones are not Microsoft O365 accounts - of course.)

Then you reproduced the problem in the way I was asked to reproduce it. Did you update your ticket with that info? Is it a bad idea to put our ticket numbers on this site?