User Impact: Users may have received a Non-Delivery Report (NDR) for external email when forwarded via the auto-forwarding feature.
More info: Users may have seen the following error when attempting to send external email via the auto-forwarding feature: "550 5.7.520 Access denied, Your organization does not allow external forwarding. Please contact your administrator for further assistance. AS(7555)"
Final status: Microsoft can confirm that re-deploying the spam rule has mitigated the impact.
Scope of impact: This affected any email being auto-forwarded externally via the feature.
Start time: Wednesday, May 26, 2021, 7:30 PM (7:30 AM UTC) End time: Thursday, May 27, 2021, 1:30 AM (5/26/2021, 1:30 PM UTC)
Preliminary root cause: A new rule inadvertently prevented external email messages from auto-forwarding.