Why Doesn’t Microsoft Graph Support Group Mailboxes?

Graph also isn’t always the best choice for broad mailbox administration. Permissions such as Mail.Send can potentially apply across a tenant, so Exchange Online RBAC for Applications is a better way to limit an application to specific mailboxes.

Be careful not to conflate group mailboxes with shared mailboxes. Shared mailboxes are backed by an account in Microsoft Entra ID, so Microsoft Graph can access them. Group mailboxes don’t have that same account relationship, which is why they aren’t supported in the same way.

The distinction explains why exporting shared inbox data through Graph works while group mailbox access doesn’t. A shared mailbox has the identity and permissions model Graph expects; a group mailbox currently lacks that foundation.

The real question may be whether group mailboxes are used heavily enough to justify the engineering effort. If their data and workflows remain relatively limited compared with user and shared mailboxes, Microsoft may not see Graph support as a high priority.