Mailbox errors: The HTTP request was forbidden with client authentication scheme 'Anonymous'.

[Polina]

The official deadline from Microsoft is July 1 2026. Until that time, please follow recommendations provided in KB4796.

Thanks

[DaStivi]

but this is also no one-time fix! as i've wrote in my posts before... my best guess is right now, when users license changes from kiosk to Ex the ews get's "nulled" and then produce errors in the backup...

the earlier we can get a GraphAPI-EXO Backup version the better!!

[Polina]

Hi Stephan,

If you get Graph API backup today, you won't be able to protect group, resource and archive mailboxes anymore as well as face a few other changes in the behavior compared to the current state of the backup you are used to.

First, we'll address the issue for limited license mailboxes. All the rest will come later. Hopefully at least some of the current limitations will be resolved/addressed by that time.

Thanks.