Error executing request. Can’t connect to the mailbox of user Mailbox database guid: <some guid> because the ExchangePrincipal object contains outdated information. The mailbox may have been moved recently. Microsoft.Exchange.Data.Storage.MailboxInfoStaleException

if you’re getting the above, on april 30th 2026 Microsoft began enforcing that the X-AnchorMailbox header contains the actual mailbox guid (and @tenantId) instead of the generic SystemMailbox{bb558c35-97f1-4cb9-8ff7-d53741dc928c} value.

This, however, is currently only enforced for specific in-mailbox commands, e.g. Get-ExoMailboxFolderPermission

If you’re using Michev’s admin api method, you may run into this 🙂