A critical outage in Microsoft’s Exchange Online service is causing email delays and “Server busy” errors for users sending and receiving emails from external domains. The issue, which was first acknowledged by Microsoft at 2:19 AM EDT, has left many wondering when normal email services will resume.
Microsoft’s investigation into the cause of the outage has identified instances where anti-spam protections are contributing to the problem, further delaying affected accounts. While the company has yet to provide a timeline for full remediation, it is working to understand the root cause and mitigate the issue as quickly as possible.
The Exchange Online service is a cloud-based email platform used by millions of users worldwide. It provides a range of features, including calendar sharing, task management, and email encryption, making it an essential tool for businesses and individuals alike. However, when the service goes down, it can have significant consequences, particularly for organizations that rely heavily on email communication.
The current outage is not the first time Microsoft’s Exchange Online service has experienced issues. In April, a similar outage prevented users from accessing mailboxes and calendars via Outlook on the web, while in June, the company addressed a service issue affecting mail flow for customers in North America, Asia-Pacific, and Europe. These incidents highlight the importance of having robust backup plans and emergency procedures in place to mitigate the impact of such outages.
While Microsoft has not disclosed which regions are currently affected by the outage or how many users are impacted, it has flagged the incident as one that involves noticeable user impact. In other words, this is a serious issue that requires urgent attention.
In related news, a recent report highlighted the effectiveness of various security measures in preventing cyber attacks. The study found that once attackers have gained valid credentials, only 37% of their actions are blocked. This emphasizes the need for organizations to prioritize multi-factor authentication and other forms of identity verification to prevent unauthorized access to sensitive data.
In light of this incident, it’s essential for users to be aware of the measures they can take to minimize the impact of an Exchange Online outage. Firstly, if you’re experiencing email delays or “Server busy” errors, try sending a new email after 24-72 hours. If the initial sender received a non-delivery report (NDR) after this period, they will need to send a new email. Additionally, consider implementing robust backup plans and emergency procedures to ensure business continuity in case of an outage.
Source: Bleeping Computer — 2026-09-04