Apple Mail (macOS Ventura) suddenly stopped deleting messages on the Exchange server

Hello,

I use Apple Mail (v16.0) on a Mac running macOS Ventura 13.6.4. In addition, I also use Apple Mail on a different work computer, as well as the Mail app on my iPhone. Occasionally I also use Outlook (v16.90.3) for work requirements.

On all of the above platforms and devices, I have two Exchange e-mail accounts: one for the university I'm currently at, and a second, which is an alumni account from a previous university.

A new problem started abruptly 4 days ago and has been consistent ever since.

When using Apple Mail on either of my computers, if I delete a message from my current university account, the message gets deleted (and moved to the Trash) LOCALLY within Apple Mail on the computer I'm using at the time, but it does NOT get deleted anywhere else.

For example, if I delete a message from my Inbox using Apple Mail on either computer, then everywhere else, including Apple Mail on the other computer, the Mail app on my iPhone, and Outlook on either computer, that message will REMAIN in my Inbox and NOT appear in the Trash.

A related problem occurs when I MOVE a message from one folder to another folder using Apple Mail on either of my computers. When I do that, a COPY of the message will show up in the new folder on all platforms on all my devices. Within Apple Mail on the computer I was using at the time, the message will be gone from the folder it was originally in (as expected), but everywhere else (Apple Mail on the other computer, my iPhone, and Outlook on either computer), I will now have two copies of the message — one in the old folder and one in the new folder.  This also started abruptly, 4 days ago.

Another related problem is an irregular behavior with my Drafts folder. The way Apple Mail normally behaves, as you're typing an e-mail, it regularly saves the latest draft to the Drafts folder. Once you send an e-mail, Apple Mail deletes any drafts from the Drafts folder. You might not ever notice this unless your computer crashes or you accidentally quit Mail — then you can find a very recent draft of the e-mail in the Drafts folder. However, starting a few days ago, drafts no longer get deleted from my Drafts folder. So, for each e-mail I now type, Apple Mail saves and stores (on the server) tens to hundreds of versions of that e-mail (depending on how long I spent on it) in my Drafts folder.

PUT SIMPLY: MESSAGES THAT SHOULD BE DELETED AREN'T BEING DELETED ON THE SERVER.

In Apple Mail Settings, under Accounts / Mailbox Behaviors, I have all boxes checked, to store everything on the server. I've used these settings for more than a decade, and nothing changed last week that could explain this sudden change in mailbox behavior.

I deleted the Exchange account from Apple Mail on one of my computers and set it up again (re-downloading all the mail), but that didn't make a difference.

To help diagnose the problem, here is a list of things that are still behaving normally:

• If I delete an e-mail from my iPhone, it gets deleted as expected everywhere, including in Apple Mail on both computers.

• If I delete an e-mail from Outlook, it gets deleted as expected everywhere, including in Apple Mail on both computers.

• My ALUMNI account from a different university continues to behave normally. Everything I described above is specifically for my CURRENT university account. If I attempt to replicate any of the problems described above with my ALUMNI account from the different university, nothing seems awry, and everything is behaving as it should, as it always has.

THEREFORE THIS APPEARS TO BE A PROBLEM WITH THE SERVER OF MY CURRENT UNIVERSITY AND HOW IT IS RECEIVING OR PROCESSING INFORMATION FROM APPLE MAIL.

I reached out to my IT support team (which does not seem to be staffed with people of the highest competence), and they replied simply that they are not aware of any changes last week that could be causing this behavior, and they noted that Apple Mail is no longer supported at my university, and they recommended that I switch to using Outlook instead.

There are many reasons I prefer to use Apple Mail, so I'm hoping someone here is brilliant enough to diagnose the problem, so that I can go back to my university's IT team with some more targeted requests for things they could investigate.

Or, if Apple Mail is choking on a process on my end, and it is somehow simultaneously affecting both of my computers but only one of my Exchange accounts, and neither Outlook nor my iPhone are affected, then I'd welcome any suggestions for how I might troubleshoot beyond what I've already laid out above.

Thanks for reading all of this!