Has anyone else recently started seeing permission problems with shared mailboxes in Outlook? The mailbox still appears and continues to populate, but opening it produces a message saying, "You do not have permission to view." Access through Outlook on the web still works. The issue is intermittent and does not affect every shared mailbox. This is happening in the EU, although it may not be region-specific.
3 Answers
We’ve been seeing similar behavior for more than a month. New Outlook and the web version usually pick up delegated mailbox access almost immediately, while classic Outlook can take several hours to recognize a newly assigned mailbox. In the meantime, we’ve been directing users to the newer client when they need access right away.
One possible explanation is permission or directory replication. Depending on how the access was assigned, Outlook can sometimes take 24–48 hours to reflect the change, even though web access becomes available sooner.
That would make sense for newly assigned permissions, but this started unexpectedly overnight on an established mailbox, so there may also be a service or client-side issue involved.
Yes, this started for us recently. Microsoft suggested that the classic Outlook client may be the cause and recommended using the new Outlook or Outlook on the web. They also provided some commands to run so we could report back with diagnostic results.
That’s odd—at least one of the affected mailboxes also fails in the new Outlook client, so it may not be limited to the classic version.

In our case, the mailbox was created about a year ago and worked normally until the problem suddenly began on Monday, so it doesn’t seem related to a new permission assignment.