This incident has been resolved.

We had an open conversation with Microsoft support but unfortunately we couldn’t find the root cause of the issue as everything started to work again as intended.

We sometimes receive some notifications from Outlook with a delay when a new email is received, which results in tickets being created with a delay. The Outlook team identified an issue that might be related and have begun building a fix, more details on their status page: https://portal.office.com/servicestatus and https://portal.office.com/Adminportal/Home#/servicehealth