Exchange Online outage delays external email

Microsoft is working to resolve an ongoing Exchange Online outage that is delaying email sent to and received from external domains.

Microsoft first acknowledged the incident, tracked as EX1467029, at 02:19 AM EDT after reports of intermittent "Server busy" errors. The company said the issue may affect users sending and receiving messages from external domains and may impact multiple mailboxes.

Microsoft said anti-spam protections may be contributing to additional delays for some affected accounts. Its initial investigation identified instances where those protections were contributing to the impact for a subset of users.

The company has not provided a timeline for full remediation. It said it is still investigating the root cause, reviewing service telemetry, and determining the most effective mitigation path. Microsoft has also not disclosed which regions are affected or how many users are experiencing problems.