Hi, I’m testing the Outlook gateway with a delegated OAuth connection and I’m trying to access a shared/delegated mailbox.
What works:
GET /outlook/v1.0/me
reading my own inbox/calendar through the gateway
active Outlook connection is valid and reconnected successfully
What does not work:
GET /outlook/v1.0/users/sharedmailbox@domain.com
GET /outlook/v1.0/users/sharedmailbox@domain.com/mailFolders/Inbox/messages
GET /outlook/v1.0/users/sharedmailbox@domain.com/calendar/events
All of those return 403:
Authorization_RequestDenied
ErrorAccessDenied
Important context:
this is a delegated connection, not app-only
the shared mailbox is visible in Outlook desktop
Exchange permissions were updated to include Full Access and Send As
after that, I deleted and recreated the Maton Outlook connection
I am calling the shared mailbox via /users//…, not /me/…
Question:
Does Maton’s Outlook integration currently support delegated/shared mailbox access through Microsoft Graph for /users/{sharedMailbox}/… endpoints?
And if yes:
are there specific delegated scopes or admin-consent requirements Maton needs for this to work?
is there any known limitation with shared mailboxes/calendar access through the Outlook gateway?
Hi, I’ve narrowed down an Outlook shared mailbox issue pretty hard.
My Maton Outlook delegated connection works fine for my own mailbox:
/outlook/v1.0/me
own inbox/calendar reads
But shared mailbox access through Maton returns 403 for:
/outlook/v1.0/users/sharedmailbox@domain.com
/outlook/v1.0/users/sharedmailbox@domain.com/mailFolders/Inbox/messages
/outlook/v1.0/users/sharedmailbox@domain.com/calendar/events
Important part:
I tested the same shared mailbox directly in Microsoft Graph Explorer and it succeeds with HTTP 200 using:
/v1.0/users/sharedmailbox@domain.com/mailFolders/Inbox/messages
So this seems to prove:
Exchange permissions are correct
delegated Graph access is working
the issue is likely in how Maton is calling/proxying Graph for shared mailboxes
Can you confirm whether the Outlook gateway fully supports delegated/shared mailbox access via /users/{mailbox}/…?
And if so, could you check whether:
Maton is using /me internally somewhere instead of /users/{mailbox}
it requires the primary SMTP or object id rather than an alias
it may be caching an older token/session after permission changes
I can provide the exact 403 responses from Maton if helpful.
Thank you for looking into it! We appreciate it. As mentioned in email, we updated our OAuth app to include the shared email scopes. Please let us know if you still have issues.
This is up and running Richard. Thank you for the quick response.