Microsoft 365 Alert – Service Degradation – Exchange Online – Some users were receiving large amounts of spam messages from specific senders in Exchange Online – RESOLVED

22/09/2023 09:07:00 AM (GMT)

NHSmail Reference : INC38423677

Microsoft Reference : EX676266

Issue Status : RESOLVED

Issue Description : Users were receiving large amounts of spam messages from specific senders in Exchange Online.

More info : This issue only affected a very specific group of organizations, and your tenancy may not have been affected. Mail may have originated from non-legitimate Microsoft domains.

Final Update : 22/09/2023 09:07:00 AM – Microsoft confirmed via an extended period of monitoring that the issue has been resolved after the implementation of their fix.

Scope of impact : Some of your users may have received large amounts of spam messages from potentially fraudulent senders in Exchange Online.

Root Cause : Microsoft’s automated Anti-Spam throttling and blocking services were not properly being triggered due to various reasons in logic. A long-term focus remains on this issue as a whole to better understand the cause and methods to address the sources of impact.

Next steps : Microsoft are reviewing their mitigation steps to reduce resolution time for similar events in the future.
They are analyzing their automated services to better improve their efficacy.