Microsoft 365 Alert – Service Degradation – Exchange Online – Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods – RESOLVED

Announcements Sourav Nandi

01/10/2025 08:50:00 AM

NHSmail Reference: INC46644509

Microsoft Reference: EX1162980

Issue Status: RESOLVED

Issue Description: Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods.

More info: Impact more heavily affects Outlook.com users.

Final Update: 02/10/2025 08:35:00 AM – Microsoft have confirmed after a period of monitoring that service availability has returned to normal levels and the backlog of messages have been processed.

Scope of impact: Users attempting to access their mailbox in one or more Exchange Online connection methods may be impacted.

Root cause: A recent configuration change unexpectedly caused a portion of infrastructure responsible for processing request flow traffic to operate below expected thresholds, resulting in impact

Next steps: Microsoft are analyzing the configuration change to better understand the cause of the impact and to help prevent similar problems in the future.