Microsoft's massive M365 outage stretches past 12 hours as its fixes keep failing

Hasn't completely ruled out cyberattack as cause of incident that's damaged Exchange Online and services that rely on it

In Australia, they’re calling it the “Microsoft long weekend” – an outage so pervasive it’s just about made Friday a write-off at organizations which rely on Redmond’s online services, especially Exchange Online.

As The Register reported yesterday, the outage started on Thursday at around 18:00 UTC and saw Microsoft 365 users unable to access email, attend Teams meetings, use cloud PCs, consult Copilot, or enjoy full access to another 15 hosted services.

The software giant says the outage impacts Microsoft 365 services “that interact with Exchange Online and email services.” Services that don’t need Exchange Online remain functional.

REG AD

The software giant initially blamed the outage on a mysterious “problem that's causing servers to fail automated health checks and become unavailable.”

REG AD

Microsoft thought it found a fix but quickly admitted “Actions taken thus far have not provided the anticipated relief.”

In the hours since, the situation has not improved markedly, and Microsoft is still struggling to restore service.

It’s also using changed the language it uses when discussing the possibility a cyberattack is the reason for the outage.

As of 04:11 UTC, the company said it could find “no indication this is the result of malicious activity.” An update time-stamped 05:46 UTC stated “As of now, we are not aware of any malicious activity that is causing this incident.”

Microsoft’s status page preserves only the company’s most recent update, but its RSS feed preserves each missive. That feed tells a tale of woe that we have distilled into lowlights and present in chronological order:

• We’re applying infrastructure capacity improvements where possible in an effort to help support traffic in regions coming online;

• We’ve monitored the status of the changes applied to improve serviceability and confirmed that change is not taking as expected;

• We’re reviewing traffic flows and affected infrastructure to identify opportunities to optimize routing. This includes verifying the reasons for service failures so we can develop specific actions to improve stability;

• We’re identifying alternate workstreams that can be applied to increase capacity in the face of sustained traffic management imbalances;

• We're observing partial recovery across regions in which we've applied these adjustments; however, these actions aren't resulting in sustained recovery;

• Current actions we are taking include scaling up virtual machines to increase capacity and reduce load. However, we are encountering issues with the machines being stuck in a bad state, preventing our changes from syncing as expected.

Microsoft’s latest status update doesn’t suggest this will be over any time soon.

“We’re continuing to pursue multiple workstreams to pinpoint the underlying cause of the traffic influx and advance the recoverability of the backend servers,” Microsoft wrote. “We’re taking a measured approach to identify and repair affected infrastructure to improve the ability to confirm the developed changes were applied. We’re tracking the results of this approach to verify the servers are showing the anticipated recovery and performance intended.”

REG AD

Hopefully, Australia and other countries in nearby time zones won’t be the only ones to get an unscheduled long weekend. ®