Mailgun incident
Microsoft Incident Resulting in Delivery Issues to M365
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Resolved after 34 minutes, on September 4, 2026.
Microsoft has resolved the underlying issue, we are seeing deliveries to M365 process normally.
Update timeline
- monitoring Sep 04, 2026, 12:20 PM UTC
Starting around 08:00 UTC, Microsoft began experiencing an incident causing an increased volume of deferred emails across all M365 regions. The affected responses are returning "451 4.7.500 Server busy". Our teams are actively monitoring the situation. No other email providers are currently affected.
- monitoring Sep 04, 2026, 12:22 PM UTC
We are continuing to monitor for any further issues.
- resolved Sep 04, 2026, 12:54 PM UTC
Microsoft has resolved the underlying issue, we are seeing deliveries to M365 process normally.
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