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

For those that missed it....

DISABLE the Thunderbird option: "SHOW ONLY SUBSCRIBED FOLDERS"

Located at: 'Tools' > 'Account Settings' > 'Server Settings' > 'Advanced' > "show only subscribed folders"

Uncheck that and then get messages and all folders will show up.

Having all folders shown is better than missing the important ones.

This provides at best an ugly hack to the problem that the last update (?) of Microsoft's MAPI (or OAuth2) implementation created in the first place.

However, this hack of changing the synchronization/subscription settings appears to work only for the Thunderbird mail client.

Be aware that a plethora of MUAs besides Thunderbird are affected. According to the other replies it has become apparent that such a solution does not exist for every email client out there.

And switching to Outlook is simply not a solution when affected users are on macOS/iOS or GNU/Linux - based operating systems.

The IMAP protocol - a de facto standard - should be adhered to, also by *Microsoft'*s implementation thereof.

Edit: It appears that the guys on the Vivaldi mail client development team have located the issue.

To my understanding Microsoft O365's IMAP implementation has dropped support for 'LSUB' without documenting this.

See their discussion: https://forum.vivaldi.net/topic/80723/lsub-failed-with-office-365-imap-server/9

Dear Michael,

 

Good day!

Thank you for posting to Microsoft Community. We are happy to help you.

 

Based on your description, I understand that you have a concern with "Unable to subscribe to Office 365 IMAP folders from MUA" At this very moment, I am looking into whether there could be a possible solution to this issue. I will get back to you as soon as I get any additional information about your query.

 

Your patience and cooperation are much appreciated.

 

Sincerely,

Ashraf | Microsoft Community Moderator

Any progress from your side Ashraf?

Morning Ian, can you please share this script you mentioned with us?
I think some of us would like to try it on our own to see if this LSUB command works or not.

You will need to have admin rights on the Azure AD for the affected O365 mailbox/tenant (as I have) - because the script uses an Enterprise Application (PopImap) which the affected account has to be able to access. You then need to obtain the Azure AD Application ID for PopImap and add it into the script.

To be honest, even if you're in a position to do that and then run the script, you're not going to see any more than I have already detailed. It is simply a question of why LSUB commands (regardless of what type of MUA is sending them) work on some O365 mailboxes and not others, even within the same tenant.

An affected mailbox of mine gives the following log file output from the script, which are the same sorts of errors MUAs are reporting:

2022-11-23T08:40:43.3261293+00:00 C 0003 lsub "" *
2022-11-23T08:40:43.3559576+00:00 S 0003 BAD LSUB failed.

2022-11-23T08:40:43.3609600+00:00 C 0004 subscribe inbox
2022-11-23T08:40:43.3898945+00:00 S 0004 BAD SUBSCRIBE failed.

2022-11-23T08:40:43.3938976+00:00 C 0005 lsub "" *
2022-11-23T08:40:43.4234356+00:00 S 0005 BAD LSUB failed.

A mailbox which works (from both Thunderbird and Outlook 2021), also works with the identical Powershell script run against it:

2022-11-23T08:42:53.2989360+00:00 C 0003 lsub "" *
2022-11-23T08:42:53.3674494+00:00 S * LSUB (\HasNoChildren) "/" Trash
* LSUB (\HasNoChildren) "/" Sent
* LSUB (\HasNoChildren \Sent) "/" "Sent Items"
* LSUB (\HasNoChildren \Trash) "/" "Deleted Items"
* LSUB (\HasNoChildren \Drafts) "/" Drafts
* LSUB (\HasNoChildren \Junk) "/" "Junk Email"
* LSUB (\HasNoChildren) "/" Outbox
0003 OK LSUB completed.

2022-11-23T08:42:53.3766586+00:00 C 0004 subscribe inbox
2022-11-23T08:42:53.5378801+00:00 S 0004 OK SUBSCRIBE completed.

2022-11-23T08:42:53.5447857+00:00 C 0005 lsub "" *
2022-11-23T08:42:53.5826269+00:00 S * LSUB (\HasNoChildren) "/" Trash
* LSUB (\HasNoChildren) "/" Sent
* LSUB (\HasNoChildren \Sent) "/" "Sent Items"
* LSUB (\HasNoChildren \Trash) "/" "Deleted Items"
* LSUB (\HasNoChildren \Drafts) "/" Drafts
* LSUB (\HasNoChildren \Junk) "/" "Junk Email"
* LSUB (\HasNoChildren) "/" Outbox
* LSUB (\Marked \HasNoChildren) "/" inbox
0005 OK LSUB completed.

Morning Ian, can you please share this script you mentioned with us?
I think some of us would like to try it on our own to see if this LSUB command works or not.

Have added Vivaldi to my Microsoft ticket as another affected MUA. Thanks.