Microsoft 365 Alert – Service Degradation – Exchange Online – Some users inbound attachment scans may be taking longer than expected to complete in Exchange Online – RESOLVED

Announcements Arpan Das

29/04/2025 09:04:00 AM

NHSmail Reference: INC46515538

Microsoft Reference: EX1063822

Issue Status: RESOLVED

Issue Description: Users’ inbound attachment scans may be taking longer than expected to complete in Exchange Online.

More info: As some safe attachment scans are getting stuck in a progress state, users” attachments may not be delivered.

As a workaround, users can forward the email messages containing undelivered attachments to themselves.

Final Update: 13/05/2025 08:25:00 AM – Microsoft have completed their validation and deployment of the previously mentioned fix, and they’ve monitored their service health telemetry to confirm that impact is remediated.

Scope of impact: Some users receiving email messages intended to have attachments may be impacted.

Root cause: A recent service update introduced a configuration issue that’s causing an index our service utilizes for querying email messages and their associated attachments to become stale. Since the index is stale, the query fails, and attachments get stuck in an in-progress state.

Next update by: Microsoft are reviewing their Exchange Online service update procedures pertaining to the indexes responsible for facilitating the impacted queries to prevent similar impact in future updates.