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Synchronization errors between Apple Mail, Calendar, and Contacts and Exchange Online on macOS Online on macOS
Disrupted – Resolved after 15h 41m
Update October 8, 2026
The outage has been resolved by Microsoft. Synchronization of Apple Mail, Calendar, and Contacts with Exchange Online on macOS is possible again.
Original message
Currently, in some cases, synchronization of Apple Mail, Calendar, and Contacts with Exchange Online on macOS is not possible. HM-IT is working to resolve the issue.
To access Exchange Online on macOS in the meantime, we recommend using Outlook for macOS: https://www.microsoft.com/de-de/microsoft-365/outlook/outlook-for-mac?market=de
Background:
Apple Mail, Calendar, and Contacts use the EWS protocol to connect to Exchange Online. As Microsoft had long announced, the protocol was shut down at the beginning of October. Apple has announced that, with a future update to macOS 27, these apps will be switched to the Microsoft Graph interface. Apple has not yet provided a date.
The use of EWS can be extended manually by having administrators add a corresponding allow list. HM-IT has taken these steps and has explicitly authorized Apple to continue using EWS.