Microsoft 365 Alert – Service Degradation – Exchange Online – Users may receive a false alert indicating their archive mailbox has exceeded or approached their storage limit – RESOLVED

06/01/2026 14:15:00 PM

NHSmail Reference: INC46717255

Microsoft Reference: EX1213825

Issue Status: RESOLVED

Issue Description: Users may receive a false alert indicating their archive mailbox has exceeded or approached their storage limit.

More info: This notification is a false alert, and users can continue working as normal as no archive mailbox storage limits have been reached.

Final Update: 22/01/2026 08:38:00 AM – Microsoft have completed the deployment of our fix for the underlying code issue and have determined that no further false alerts associated with this issue have occurred since January 15th, 2026..

Scope of impact: Your organisation is affected by this event, and some users may receive a notification indicating their archive mailbox has exceeded or approached their storage limit.

Root cause: A recent code regression in the Exchange Online service caused the alerting logic for auto‑expanding archive mailboxes to incorrectly evaluate mailbox size thresholds, leading to incorrect alert notifications.

Next steps: Microsoft are reviewing our update testing and validation methods to better identify code issues such as this prior to deployment to prevent similar impact in the future.