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

[aeph]

Hi all,

since today we are getting strange error messages on Mailbox-objects: "The HTTP request was forbidden with client authentication scheme 'Anonymous'.".

We haven't changed anything - not all Mailbox objects are affected.

We are running on 8.1.2.3301 - modern application setup is used.

Does anyone else have this problem?

CaseID: #07892767

[megawatt_ak]

same problem arose yesterday 11/18/25 ... 1 user ...

ver 8.1.2.180

Following for the fix

[ReKe]

We are on 8.2.0.2202 and see it also with Veeam Data Cloud.

Case # 07892442

[DaStivi]

I’ve also noticed a few jobs/customers starting to fail with this new error — only a handful so far, but it’s concerning.

[rsk@mb-solutions.dk]

Also seeing this error on 1 of our many customers.

[aeph]

Has anyone been able to find a solution or fix the error? Veeam suggests reauthenticating the organization, but this would require the customer's assistance (global admin).

[MSavp]

We see the same problem with some of our M365 items. Some do seem to be working though. We have v8.1.2.180 installed.