When a user tries to cancel or modify a calendar for another user they recieve a NDR with the following message

‘554 5.2.0 STOREDRV.Deliver.Exception:QuotaExceededException.MapiExceptionShutoffQuotaExceeded

Regular emails and new calendar invites come through fine.

MS support recommended clearing her recoverable items from trash

There was a Global Retention Policy Turned on in the Tenant so we could not delete recoverable items. We enabled archive Mailbox for the users with auto expanding archive and ran managed folder assistant manually which solved the issue

There is a process called “Dumpster Quota Enforcer” which is also part of the Managed Folder Assistant. This functions to help prevent mailboxes from hitting the Recoverable Items Quota (30GB default, automatically increased to 100GB if a Hold is applied, increased to 110GB if Auto-Expanding Archive is enabled at the mailbox level)