A Microsoft 365 outage that began Thursday was still affecting Exchange Online mailbox connections on Friday, with Microsoft reporting that the incident had not ended as of its 4:59 a.m. UTC update. The company said Outlook on the web and several connection methods used by email apps and services could be affected.

The disruption has also affected other Microsoft 365 services, according to Microsoft’s incident notices. The latest update described ongoing infrastructure work and persistent traffic imbalances; it did not give an estimated resolution time.

Which Outlook and Microsoft 365 connections are affected?

Microsoft’s Exchange Online notice lists Outlook on the web, Messaging API (MAPI), Exchange ActiveSync and the Representational State Transfer (REST) API among the connection methods that may be affected. Those interfaces support Outlook access across browsers, desktop and mobile clients, and connected services, so the incident can appear differently depending on how an account is accessed.

Microsoft’s separate Microsoft 365 service notice covers impacts beyond Exchange Online. Reuters reported Thursday that users also reported problems with Teams and Microsoft 365, while the Associated Press described a broader disruption affecting several Microsoft apps. Those early user reports came from outage trackers and should not be read as a count of confirmed affected accounts.

Microsoft says recovery work is ongoing

In its latest Exchange Online update, Microsoft said it was adding virtual-machine capacity and trying to synchronize network changes on machines in a bad state. Earlier, the company reported partial regional recovery after traffic adjustments, but said the improvement was not sustained.

Microsoft also said in an earlier update that it had no indication the disruption resulted from malicious activity. That is the company’s assessment as of that notice, not a final public explanation of the outage’s root cause; its incident report still listed the root cause as unavailable.

Where to check service status

People who rely on Outlook or other Microsoft 365 apps can check Microsoft’s public service-status page for updates. Organizations with Microsoft 365 administrator access can also consult the Service Health section of the admin center, where Microsoft posts service-specific incident details. We’ll update this report if Microsoft posts a material change to the incident status.

See more coverage in The Globuzz Tech section.

Sources: Associated Press; Reuters, republished by Investing.com; Microsoft incident notifications mirrored by PennO365; Microsoft public service status.