Microsoft has fixed an Exchange EWS issue from March 14, 2024 on Macs

Exchange Logo[German]A small addendum from this week. A reader emailed me a few days ago to say that there was a problem with Microsoft Exchange in connection with a mail client with EWS. According to the reader's observations, this has been occurring since 14.3.2024: Mail clients only sporadically connect to Exchange EWS on the Mac. Here is some information about the "permanent construction site" Microsoft Exchange connection on the Mac, which I had already taken up in the blog. The problem should have been resolved since March 19, 2024.


The error description

German blog reader Frank had already contacted me by email on March 18, 2024 and outlined the problem from his point of view. He wrote to me that there had been problems connecting mail clients with EWS since Thursday, March 14, 2024 – which, as it turns out, relates to Apple Mac systems. Frank writes that a company he supports operates Microsoft 365 Business Premium with around 70 accounts.

In this constellation, he is aware of at least two accounts at the customer that connect to EWS. EWS stands for Exchange Web Services, a cross-platform API that enables applications to access mailbox elements, e.g. email messages, appointments and contacts, from Exchange Online, Exchange Online as part of Office 365 or from local Exchange versions starting with Exchange Server 2007.

The environment of the customer: They are using Mac systems that access EWS once with Mac Mail and once with the EMClient (the latter system is Frank's Mac). This causes serious problems, which manifest themselves as follows: These affected clients only get a connection to their mailbox very sporadically, if at all, from early morning to early evening.

The funny thing is that from about 17:00/18:00 it works without any problems, writes Frank. This was the case the previous week on Thursday and Friday and last weekend, when there were no problems and the Macs were connected to EWS. The statement: "it was probably working all the time – since this morning [18.3.2024] it is not working again".

Frank wrote that he cannot retrieve status e-mails that he receives overnight with EWS. The reader described another observation to me: "Interesting, I have 2 mailboxes with the customer. One mailbox always works with EWS. And the other mailbox, as described above, has not always worked since Thursday." Frank says that the connection with ActiveSync works without any problems. The same applies to the connection with Outlook for Mac. Frank concluded his email with: "From an admin point of view, I can only advise the customer to use Outlook on his Mac until M$ has solved the problem."


Wasn't there something?

Frank's message has been left lying around for a while, but when I read his text, something rang a bell. On March 20, 2024, I had published the German blog post Outlook-Probleme unter macOS seit Mitte März 2024?, because I wan't to see, if more readers are experiencing this issue. The post was based on some reader feedback on Facebook and in my German the blog, which roughly addressed "problems with Outlook on the Mac". Falls into the same category of bugs as Frank describes above – though Frank narrows it down to EWS – after all, one criticism of the blog post was that it wasn't clear which clients were being used.

Is it fixed now?

In this comment, Frank wrote that the problem had probably been fixed by Microsoft as of March 19, 2024. Another user confirmed that the problem had been fixed. Question: Does anyone have any information on what caused the EWS problems?

In another comment a German blog reader told me, that the issue hasn't been fixed officially. He posted the following text from the admin center:

Legacy Outlook for Mac users may be unable to connect to their Exchange Online mailboxes
Title: Legacy Outlook for Mac users may be unable to connect to their Exchange Online mailboxes

User impact: Legacy Outlook for Mac users may be unable to connect to their Exchange Online mailboxes.

More info: Impact is specific to those who are on version 15.20 and builds 7409.15 or below. As the fix progresses throughout our safe deployment processes, admins can check if they're on builds 7409.16 or above to validate if they've received the fix or not by running the following cmdlet:

Get-Mailbox TestUser | fl *version*

The cmdlet produces an "AdminDisplayVersion" output which delineates which version a user is on.

Current status: As we continue to monitor the fix deployment, we've assessed that the deployment process is taking longer than originally anticipated. We expect the aforementioned process to be completed by our next scheduled update.

Scope of impact: Users on the legacy Outlook for Mac client that's on version 15.20 and builds 7409.15 or below may be impacted.

Start time: Friday, March 15, 2024 at 9:00 AM GMT+1

Estimated time to resolve: We expect the deployment process to be completed by Friday, March 22, 2024 at 11:00 PM GMT+1.

Root cause: A recent service maintenance change introduced a code issue that inhibits communication between legacy Outlook for Mac users and the Exchange Online service, which is resulting in the impact.

Next update by: Friday, March 22, 2024 at 11:00 PM GMT+1

Similar issues:
Exchange Server security updates (March 12, 2024)
Fix for connection issues with Microsoft 365 apps (March 2023)
Problems with Microsoft Outlook and Exchange since March 2024 patch day? – Part I
Issues with Microsoft Outlook (scheduling) since March 2024 patchday? – Part II
Microsoft 365 connection issues: Outlook shows red exclamation mark

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