01
Confirm the mailbox object
Verify that the target is actually the intended shared mailbox and not an alias, distribution list, user mailbox, or similarly named object.
Everyday IT · Shared Mailbox
Prove the permission before rebuilding Outlook.
A shared mailbox can be configured correctly in Microsoft 365 and still take time to appear in the desktop client.Separate delegation, propagation, auto-mapping, and local Outlook state.
The four checks
Do these before deleting profiles or repeatedly removing permissions.
02
Confirm Full Access
Reading the mailbox requires the correct access permission. Send As and Send on Behalf are separate and do not by themselves make the mailbox appear.
03
Allow propagation
New delegation may not appear immediately. Repeatedly removing and re-adding the same permission can restart the waiting period and muddy the evidence.
04
Compare web vs desktop
If the mailbox is accessible through Outlook on the web or another clean path, the cloud permission is likely working and the remaining issue is local client state.
When auto-mapping does not behave as expected
The mailbox may be healthy even when it does not appear automatically.
Outlook restart
Refresh the client first
Close Outlook completely and reopen it after sufficient propagation time before making larger changes.
Profile state
One profile can be the broken layer
If the mailbox works elsewhere but not in one Classic Outlook profile, treat the local profile, cache, or Office identity as the next layer.
Manual access
Use deliberate configuration when appropriate
Where the organization’s design allows it, manually opening or adding the shared mailbox can help distinguish auto-mapping behavior from permission failure.
History missing
Visibility is not the same as mailbox completeness
If the mailbox appears but older content is missing, investigate mailbox state, retention, recovery, archive, or synchronization instead of assuming delegation is wrong.
What not to do
Keep the test controlled.
Do not
Toggle permissions repeatedly
Verify the current object and permission first, then allow the change time to propagate.
Do not
Reset the user's password
A missing delegated mailbox is not normally solved by changing the primary user's password.
Do not
Rebuild Outlook before proving the cloud side
A profile rebuild is useful only after you have evidence that the mailbox and delegation work elsewhere.
Escalate
When mailbox state is uncertain
Pause when the mailbox may have been deleted, restored, relicensed, converted, or affected by retention requirements that need a deliberate recovery plan.
Permission first. Client second.