Two weeks ago, the company linked a weekend Microsoft 365 outage affecting Outlook and Exchange Online authentication to another "code issue." A subsequent advisory revealed that Exchange Online users still had issues accessing calendars and email messages using the iOS native mail app. The company first acknowledged the Exchange Online email delivery issues on March 10, 11:14 AM, but the admin center incident report says the outage started on March 7, 12:30 PM UTC. Microsoft says it partially mitigated a week-long Exchange Online outage causing delays or failures when sending or receiving email messages. Customers worldwide also reported experiencing email delivery failures over the last week, with those impacted saying they were receiving a Non-Delivery Report (NDR) with a "554 5.6.0 Corrupt message content" error. This second incident is still ongoing, with the company saying it's "limited to a small subset of messages" that trigger NDR failures and intermittent plain text calendar invite emails with winmail.dat attachments. While the company didn't publicly share information on this incident, it tagged it as a critical service issue tracked under EX1027675 on the Microsoft 365 Admin Center. "A recent service update, intended to improve our message transport services, introduced a code issue that resulted in impact for a portion of service infrastructure," Redmond said in the final update regarding this incident on Thursday. Although it is still working on finding the root cause of these email delivery failures, Redmond says it's testing a potential fix deployed on an isolated section of its infrastructure. "Additionally, users may be unable to send email messages with attached files in any connection method of Exchange Online.
This Cyber News was published on www.bleepingcomputer.com. Publication date: Fri, 14 Mar 2025 19:00:22 +0000