Outage in Mailjet
Microsoft Incident Resulting in Delivery Issues to M365
Resolved MinorIncident Report
Summary AI Generated
A Microsoft-side incident beginning around 08:00 UTC caused elevated email deferral rates for all M365 regions, with servers returning "451 4.7.500 Server busy" errors. Only M365 recipients were affected; all other email providers remained unimpacted. The incident lasted approximately 33 minutes and was fully resolved by 12:55 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.
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Latest Updates ( sorted recent to last )
RESOLVED
4 days ago - at 09/04/2026 12:55PM
This incident has been resolved.
MONITORING
5 days ago - at 09/04/2026 12:23PM
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.
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