Microsoft 365 Alert – Service Degradation – Exchange Online – Users may be unable to open some attachments from email messages in some Exchange Online connection methods – RESOLVED

Announcements Sourav Nandi

03/03/2025 09:00:00 AM

NHSmail Reference: INC46465079

Microsoft Reference: EX1020077

Issue Status: RESOLVED

Issue Description: Users may be unable to open some attachments from email messages in some Exchange Online connection methods.

More info: Files attached directly to the emails as invite attachments are affected. Cloud file attachments appear to be unaffected by this issue. This issue also appears to be limited to the Outlook mobile app for iOS and Android as well as Outlook for Mac.

Final Update: 06/03/2025 09:00:00 AM –The process of reverting the problematic service update is complete, and Microsoft telemetry confirms that this issue is resolved.

Scope of impact: Some users may have been affected when trying to open some attachments from email messages in Exchange Online.

Root cause: A recent service update contained a code regression that resulted in impact.

Next Steps: Microsoft are reviewing their service update testing and validation procedures to better detect and prevent issues like this prior to deployment in the future.