Microsoft 365 Alert – Service Degradation – Exchange Online – Some users may be unable to view mailbox storage data in Outlook and Outlook on the web – ONGOING

16/07/2026 08:36:00 AM

NHS.net Connect Reference: INC46881346

Microsoft Reference: EX1428537

Issue Status: ONGOING

Issue Description: Some users may be unable to view mailbox storage data in Outlook and Outlook on the web.

More info: Affected users are shown the following error message “Storage data is temporarily unavailable” when trying to view mailbox storage data for multiple mailboxes.

Current Update: 16/07/2026 08:38:00 AM – Microsoft has identified that a recent service build introduced an unsupported property into mailbox statistics data. When the service attempted to retrieve mailbox storage information, the unsupported property caused the request to fail and prevented mailbox storage data from being displayed. We’ve deployed a code fix to remove the unsupported.

Scope of impact: Some users attempting to view mailbox storage data in Outlook and Outlook on the web may be impacted. This information may be updated as our investigation continues.

Root cause: A recent service build introduced an unsupported property into mailbox statistics data returned by a backend process. When the service attempted to retrieve mailbox storage information, the unsupported property caused the request to fail and prevented mailbox storage data from being displayed.

Next update by: Wednesday, July 22, 2026, at 1:30 PM UTC