Microsoft 365 Alert – Service Degradation – Exchange Online – Users may be unable to send Exchange Online email messages – RESOLVED

Announcements Habiba Tabasum

28/02/2025 06:10:00 PM

NHSmail Reference: INC46464384

Microsoft Reference: EX1019763

Issue Status: RESOLVED

Issue Description: Some users are unable to send Exchange Online email messages.

More info: Affected users’ email messages may be stuck in a pending state and preventing them from being delivered.

Final Update: 03/03/2025 09:12:00 AM – Microsoft have determined that the code fix deployment has completed, and after a period of monitoring, they have confirmed the impact was remediated.

Scope of impact: Impact is specific to users who are served through the affected infrastructure.

Root cause: A recent service update switched the email transport infrastructure to an unexpected authentication method, causing a conflict that prevented email from being delivered.

Next update by: To help prevent similar impact in the future, Microsoft are further reviewing their update release procedures to more quickly identify these types of issues before deployment.