Mailgun incident

Microsoft Incident Resulting in Delivery Issues to M365

Notice Resolved View vendor source →

Mailgun experienced a notice incident on September 4, 2026, lasting 34m. The incident has been resolved; the full update timeline is below.

Started
Sep 04, 2026, 12:20 PM UTC
Resolved
Sep 04, 2026, 12:54 PM UTC
Duration
34m
Detected by Pingoru
Sep 04, 2026, 12:20 PM UTC

Update timeline

  1. 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.

  2. monitoring Sep 04, 2026, 12:22 PM UTC

    We are continuing to monitor for any further issues.

  3. resolved Sep 04, 2026, 12:54 PM UTC

    Microsoft has resolved the underlying issue, we are seeing deliveries to M365 process normally.