Microsoft 365 Alert – Service Degradation – Exchange Online – Users’ inbound email messages from are quarantined in Exchange Online when they contain attachments – RESOLVED

09/05/2025 08:50:00 AM

NHSmail Reference: INC46524704

Microsoft Reference: EX1069669

Issue Status: RESOLVED

Issue Description: Users’ inbound email messages from are quarantined in Exchange Online when they contain attachments.

Final Update: 13/05/2025 08:25:00 AM – Microsoft have completed their restoration process and have recovered all possible email messages impacted by this event. Any email messages not released at this time were confirmed to be truly malicious and not removed from quarantine.

Scope of impact: Your organization is affected by this event, and some users are impacted when receiving messages containing attachments.

Root cause: A recently enabled signature utilized by our machine learning model to detect malicious email messages contained a misconfiguration, resulting in impact.

Next steps: Microsoft are investigating opportunities to improve impact detection when enabling signatures utilized by their machine learning model and better prevent similar future impact.