Issue Reported: 26/05/2021 11:05:00 AM
Microsoft Reference : EX258320 / EX258379
Issue Status: RESOLVED
Issue Description: We are aware of an issue wherein users may receive a Non-Delivery Report (NDR) for external email when forwarded via auto-forwarding feature.
Users may see 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)”
Scope of impact: Your organization is affected by this event, and any user expecting to receive an auto-forwarded message sent between Wednesday May 26, 2021, at 7:30 AM UTC and 1:30 PM UTC, may be impacted.
Final Update – 31/05/2021 05:58:00 PM: A recent impact caused auto-forwarded messages to return NDRs. This event was communicated under EX258320 and was resolved by redeploying a spam rule, which had been found to be causing impact.
While Microsoft are focused on a long-term mitigation, these messages can be successfully received when manually forwarded. After extensive monitoring of telemetry, Microsoft have confirmed that the efforts to reprocess and deliver the affected messages were successful and service is restored.