Users may experience delays sending and receiving email messages

Title: Users may experience delays sending and receiving email messages

User impact: Users may experience delays sending and receiving email messages.

Current status: The new throttling rule has successfully been deployed. We’ve received confirmation from some of the previously affected users that they can now send and receive email. Additionally, our telemetry shows that the new throttling rule is having the desired effect and providing relief.

Scope of impact: Some users who are located in Europe attempting to send or receive Exchange Online email messages may be impacted.

Start time: Friday, August 29, 2025, at 10:36 AM UTC

Root cause: An increase in internal service to service calls resulted in authentication failures, causing email delays and failures.

Next update by: Friday, August 29, 2025, at 4:00 PM UTC

The original throttling rule did not have the desired effect due to a configuration issue. We’re deploying a new throttling rule with an alternate configuration to remediate impact.

This quick update is designed to give the latest information on this issue.

We're monitoring the email delivery telemetry as the call throttling mitigation measures take effect.

This quick update is designed to give the latest information on this issue.

Title: Users may experience delays sending and receiving email messages

User impact: Users may experience delays sending and receiving email messages.

Current status: After analyzing diagnostic data we determined that excessive internal service-to-service calls resulted in authentication failures, causing email delays and failures. We’re throttling these calls to mitigate the issue and provide relief.

Scope of impact: Some users who are located in Europe attempting to send or receive Exchange Online email messages may be impacted.

Start time: Friday, August 29, 2025, at 10:36 AM UTC

Root cause: An increase in internal service-to-service calls resulted in authentication failures, causing email delays and failures.

Next update by: Friday, August 29, 2025, at 3:00 PM UTC

Title: Users may experience delays sending and receiving email messages

User impact: Users may experience delays sending and receiving email messages.

Current status: We're reviewing service monitoring telemetry to isolate the source of the issue and establish a fix.

Scope of impact: Some users who are located in Europe attempting to send or receive Exchange Online email messages may be impacted.

Next update by: Friday, August 29, 2025, at 2:30 PM UTC

Title: Users may experience delays sending and receiving email messages

User impact: Users may experience delays sending and receiving email messages.

Current status: We're investigating a potential issue and checking for impact to your organization. We'll provide an update within 30 minutes.

Scope of impact: Impact is specific to a subset of users who are accessing the service from Europe.