Microsoft is investigating a widespread Exchange Online outage disrupting mail flow for customers in North America and Germany. Users face significant sending and receiving delays with some messages undelivered for over an hour while engineers seek the root cause.
As of June 3, incident EX1331830 remains active and unresolved, affecting expanded regions including APAC and Europe. Microsoft is evaluating targeted service infrastructure resets as potential mitigation and analyzing mail queue backlogs for root cause.
Some affected users are seeing temporary SMTP deferral errors stating "The maximum number of concurrent connections per resource forest has exceeded a limit, closing transmission channel."
Admins should check the Microsoft 365 admin center service alert for EX1331830 and prepare for potential SMTP retry configurations during the ongoing incident.
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