[German]I'm posting an observation here in the blog that a reader pointed out to me – a second reader also seems to be affected. Administrators of Exchange Online tenants have noticed since around May 14, 2025 that they can no longer make changes to the mailboxes. Adjusting permissions is therefore impossible.
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Reader information on the problem
German blog reader Dennis F. contacted me by e-mail on the evening of May 15, 2025 and wrote under the subject "Exchange Online problems" that he was having trouble as a tenant administrator of Exchange Online mailboxes or accounts.
The reader and his colleagues in IT have been observing for several days that in at least three Microsoft 365 customer tenants no changes are possible within the respective mailboxes.
According to his statement, it is no longer possible to set up redirects in the Admin Center, for example. It is also not possible to set full access permissions, let alone retrieve the permissions.
The behavior can also be reproduced within Outlook. For example, no granular e-mail folders or contacts can be shared with other accounts there. For example, the following error message (here in German) appears in the Admin Center of the Exchange Online Tenants:
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A message informs the tenant admin that the changes to the settings could not be saved. There are some more details about the error, which indicate that the administrator does not have the authorization to make changes. The cause is often that the target forest is not included in the account partition of the source forest.
When trying to configure a delegation for a mailbox, the above message appears with a reference to an error when retrieving the mailbox authorizations, together with the statement that Microsoft has a problem with the server. You should try again later – but that probably won't help.
The reader also wrote that a support case was pending at Microsoft, but that it was being handled more slowly than effectively. For example, IT was asked for a network recording from the Edge Browser, as well as a recording of the steps performed with the PSR tool (problem step recorder). Screenshots of the domain controller error message from various customer tenants had already been provided beforehand, which directly showed the source of the problem. However, this information was ignored by Microsoft Support.
Another affected person?
Blog reader Dennis F. asked to post the above information on the blog and to ask whether others are also affected. This appears to be the case, as the German blog post Exchange Online- und MS365-Probleme durch Schwachstelle? (März 2025), blog reader habogus posted this German comment on May 16, 2025. The user realized that his comment on the above article was off topic, but wrote that "one of the most useful and up-to-date" articles on this was my blog post.
He wrote that "as of today" he (or the team of tenant administrators) can no longer assign user rights, i.e. delegation, in any shared mailbox. The same applies to a personal mailbox.
Furthermore, the user notes that SharePoint is also spinning in some places. Pages assigned to a hub are not assigned as usual. The pages seem to ignore their hub, the reader writes and asks whether other administrators might also have problems. That sounds like the above description to me.
Microsoft Incident EX1072592
I had a look, there is an incident report EX1072592 from Microsoft dated May 13, 2025, which states that a recent service update to fix an unrelated service issue resulted in a serious code regression. This is preventing some users from using Exchange Online auto-forwarding. I'm not sure if this fully addresses the issue above though.
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