Microsoft is investigating an ongoing Exchange Online outage that is causing delays when users send and receive email messages to and from external domains.
The incident is being tracked as EX1467029. Microsoft acknowledged the issue at 2:19 a.m. EDT after receiving reports of intermittent “server busy” errors affecting Exchange Online customers.
“This issue affects users who are trying to send and receive email messages from external domains in Exchange Online,” Microsoft said in a service alert seen by BleepingComputer. “Users may experience intermittent ‘server busy’ errors, which may affect multiple mailboxes.”
According to Microsoft, anti-spam protections may be contributing to the ongoing Microsoft 365 email delays by slowing message processing for some affected accounts.
Microsoft has not provided an estimated time for a complete resolution. The company is continuing to investigate the root cause and said it will share additional information as it becomes available.
“Our initial investigation has identified instances where anti-spam protections may be impacting some users,” Microsoft added.
“We continue to analyze behavior and review service telemetry to better understand the root cause and determine the most effective mitigation measures.”
Microsoft has not disclosed how many customers or which regions are affected by the Exchange Online service disruption. However, the company typically opens service incidents when an issue has a noticeable impact on users.
In April, Microsoft resolved another 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. Exchange Online access problems have also intermittently affected Outlook mobile and macOS users in recent weeks.
Most recently, in June, Microsoft addressed a similar service issue that disrupted email flow for customers in North America, Asia Pacific (APAC), and Europe.
Earlier this week, Microsoft also mitigated a major Microsoft 365 outage that caused authentication failures, connectivity problems, service delays, and other service disruptions.
This is a developing story and will be updated as more information becomes available.
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Source: www.bleepingcomputer.com