Resolved after 5 hours 3 minutes, affecting Inbound Email Security and Outbound Email Security, on September 4, 2026.
We're no longer observing live deferred events. We're continuing to monitor the situation.
Affected components
Update timeline
- investigating Sep 04, 2026, 10:09 AM UTC
We're seeing slower delivery into O365 for Mesh customers. We're currently investigating.
- investigating Sep 04, 2026, 10:37 AM UTC
Outbound Relay also appears to be affected. Only for traffic going to Office 365
- identified Sep 04, 2026, 11:12 AM UTC
This appears to be related to an ongoing issue on Microsoft 365s infrastructure. It can be tracked via the below link. https://admin.cloud.microsoft/?#/servicehealth/:/alerts/EX1467029
- monitoring Sep 04, 2026, 01:00 PM UTC
We're beginning to see improvements with delivery into Microsoft 365's infrastructure. We are still seeing some messages being given a deferral by them. They have acknowledged the issue publicly and that they are applying mitigations. We'll continue to monitor and post updates. https://x.com/MSFT365Status
- resolved Sep 04, 2026, 03:12 PM UTC
We're no longer observing live deferred events. We're continuing to monitor the situation.
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