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We want to share mailboxes with 'Least privilege' principle.
So when creating a shared mailbox instead of making users Owner we want to assign only permissions on the necessary folders.
With a PowerShell session to Exchange Online we make the following changes:
Add-MailboxFolderPermission -Identity SharedMailboxTest:\ -user ******@contoso.com -AccessRights Reviewer
Add-MailboxFolderPermission -Identity SharedMailboxTest:\Inbox -user ******@contoso.com -AccessRights Reviewer
This works fine with Outlook Web App and Outlook desktop client. We can add the shared folder and read the messages.
But when we try to add a shared folder on a Outlook Mobile client we get an error:
Authentication failed
That didn't work. You may not have the right permissions to add this mailbox or this mailbox doesn't exist.
Also added permission directly on the mailbox:
Add-MailboxPermission -Identity SharedMailboxTest -User ******@contoso.com -AccessRights ReadPermission
But that didn't make a difference.
It must be possible to delegate folder permissions. It works for default clients, but it refuses to work on mobile Outlook unless I give the user Owner permissions, but that is not 'Least privilege'.
What I'm I missing here or did I stumble on a bug in Outlook Mobile?
(It has to be Outlook mobile client on cell phones)
Using Classic Outlook on Windows for personal email, calendar, and contact management
Locked Question. This question was migrated from the Microsoft Support Community. You can vote on whether it's helpful, but you can't add comments or replies or follow the question.
9/11/2021 PST 1:23PM and still having this issue. Any word on this? I would hate to have to convert the sharedmailboxes back to mailboxes.
Thanks Mike. Where did you log the issue?
I just tested and you're right, still broken.
Any update on this? It's now September 11th and this is still not working. This is business critical for us.
For the interested folks.
This is the answer I got from Microsoft. They are planning to release a fix on Sept. 10th 2021 at 8:30PM UTC (4:30PM EST)
________________________________________________________________________________
Title: Users can't add shared mailboxes via the Outlook mobile app
*User Impact: Users are unable to add shared mailboxes via the Outlook mobile app.**More info: Outlook desktop and Outlook on the web are unaffected.Users will encounter the following error when attempting to add shared mailboxes via the Outlook mobile app:"Authentication Failed: That didn't work. You may not have the right permissions to add this mailbox or the mailbox doesn't exist."**Current status: We've determined that the reversion of the offending change across the affected environments requires additional validation and processing time, and we now anticipate resolution by Friday, September 10, 2021.**Scope of impact: Any user attempting to add shared mailboxes via the Outlook mobile app may be impacted.Start time: Tuesday, August 24, 2021, at 7:00 AM UTCEstimated time to resolve: We expect the change will be reverted and the user impact will be mitigated by Friday, September 10, 2021.*Root cause: A recent update intended to optimize the error code for disabled accounts incidentally introduced an incorrect logic and caused impact. Next update by: Friday, September 10, 2021, at 8:30 PM UTC