Full Access
Open and manage the mailbox
This controls whether the user can open and work inside the shared mailbox. It does not automatically mean they can send as that address.
Everyday IT · Shared Mailboxes
Opening the mailbox and sending from it are different permissions.
Shared mailbox tickets drag on when access is treated as one switch.Full Access, Send As, and Send on Behalf solve different problems.
Send As
Message appears from the mailbox
Use this when the recipient should see the shared mailbox as the sender.
Send on Behalf
Sender relationship remains visible
Use this when the message should indicate that the user sent on behalf of the shared mailbox.
Do not fight propagation
Cloud permissions can take time to appear in Outlook or auto-mapping.
1
Confirm the right permission exists
Check the mailbox object and the user's assigned permission before rebuilding Outlook.
2
Allow reasonable propagation time
A newly assigned permission may not appear immediately. Repeatedly removing and re-adding access can make the state harder to understand.
3
Test the actual requested action
Opening the mailbox, sending as it, and receiving group mail are separate tests.
4
Move local only after cloud state is proven
If the permission is correct and enough time has passed, then investigate Outlook profile, cache, auto-mapping, or manual mailbox addition.
Verify the permission before repairing the client.