Microsoft says it is testing a fix to an outage affecting Exchange Online and Outlook, lasting for 17+ hours from around 11:30AM ET on Monday (Sarah Perez/TechCrunch)

Microsoft experienced an outage affecting Exchange Online and Outlook on Monday, which started around 11:30 AM ET and lasted for over 17 hours. The outage caused email delays and failures, authentication issues, and other problems. According to TechCrunch, Microsoft confirmed the issue at 12:43 PM ET and identified a problem with an authentication component.

Microsoft said it was testing a fix for the outage, which affected not only Exchange Online but also other services. The company reported that it was working on a remediation strategy and would roll out the solution more broadly if it proved successful. Mashable reported that Microsoft 365 status account posted an update on X, stating that it was continuing to deploy its mitigation across the affected environment and users should begin to see gradual recovery to mail flow.

The outage was reported by users on sites like Downdetector, with some customers responding to Microsoft's update by asking for more specifics on timing. According to TechCrunch, the outage highlighted how much of the business world still relies on email, particularly Outlook and Exchange.

Brief written by urgent.news from Techmeme, Mashable, TechCrunch — 3 reports on this story. Machine-written — may contain errors; check the original before relying on it.