Microsoft 365 Alert – Service Degradation – Microsoft Defender XDR – Users may experience delays and see failures with multiple functions in Microsoft Defender – RESOLVED

20/04/2026 9:20:00 AM

NHSmail Reference: INC46803089

Microsoft Reference: DZ1283890

Issue Status: RESOLVED

Issue Description: Users may experience delays and see failures with multiple functions in Microsoft Defender.

More info: Some users may experience delays and failures with the following functions:
– Threat Explorer
– Defender Portal explorer
– Email entity
– Advanced hunting

Final Update: 22/04/2026 08:22:00 AM– Microsoft has cleared the resulting processing backlog requests and confirmed, following a period of monitoring service health telemetry, that impact has now been remediated.

Scope of impact: This event could impact some Microsoft Defender users serviced through North America, who are attempting to utilize functions such as Threat Explorer, Defender Portal explorer, Email entity, and Advanced hunting. This section may be updated as our investigation continues.

Root cause: Increased traffic to a portion of the service infrastructure is causing failures for users who are attempting to utilize functions such as Threat Explorer, Defender Portal explorer, Email entity, and Advanced hunting and is resulting in this impact

Next Steps: Microsoft are analyzing performance data and trends on the affected infrastructure to help prevent this problem from happening again.