Microsoft is working to resolve an ongoing Exchange Online outage that is slowing email sent to and received from external domains.
The company first acknowledged this incident (tracked under EX1467029) at 02:19 a.m. EDT when he began investigating intermittent “Server Busy” error messages.
“This issue affects users who may be trying to send and receive email messages from external domains in Exchange Online. Users may experience intermittent ‘Server is busy’ errors affecting multiple mailboxes,” Microsoft said in a service alert seen by BleepingComputer.
“Depending on the client, the service should periodically try to resend the email that was previously affected. If the original sender received an NDR after 24-72 hours (different email clients or providers may vary), they will need to resend the email.”
Microsoft says these ongoing email issues may be exacerbated by spam protections further slowing down affected accounts.
The company did not provide a timetable for a full fix, saying it was still investigating the issue to determine the root cause and would provide additional details later today.
“Our initial investigation identified instances where spam protection may have contributed to impacting a subset of users,” the company added. “We continue to analyze behavior and review service telemetry to better understand the root cause and determine the most effective mitigation path.”
While Microsoft has not yet disclosed which regions are affected by this ongoing outage or how many users are affected, it is labeling it as an incident that typically involves a noticeable impact on users.
In April, Microsoft also allowed an Exchange Online outage that prevented users from accessing mailboxes and calendars through Outlook on the web, Outlook desktop, Exchange ActiveSync, and other Exchange Online connection protocols. and Exchange Online mailbox access issues that intermittently affected Outlook and macOS mobile users for weeks.
Most recently, in June, it addressed a similar service issue affecting mail flow for customers in North America, Asia Pacific (APAC), and Europe.
Earlier this week, on Thursday, it also mitigated a massive outage that caused authentication issues, connection issues, service delays and crashes, and other problems for Microsoft 365 customers.
Update on September 04, 10:26 a.m. EDT: Microsoft says issue EX1467029 is resolved for new emails.
“Telemetry shows that the service is working as expected for new emails, and this is consistent with organizations confirming that the issue is no longer occurring,” Microsoft said. “We are monitoring email queues and performing final checks to confirm the issue is fully resolved.”
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