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How to Fix Microsoft 365 Error 451 4.3.2 Temporary Server Error (January 2026)

Are you unable to send or receive emails today? Many Microsoft 365 users in the US, UK, and Canada are reporting a "451 4.3.2 Temporary Server Error" when trying to access Outlook or Microsoft Teams. This global outage, which peaked on January 22nd and continues to affect some regions today, January 23, 2026, is causing major disruptions. Here is what the error means and how you can manage it.

​What is the Microsoft 451 4.3.2 Error?

​The "451 4.3.2" error is a server-side response indicating that the Microsoft 365 mail server is temporarily overloaded or experiencing a configuration glitch. This specific incident is linked to a massive outage that impacted Outlook, Microsoft Defender, and Microsoft Purview. When the server cannot process your request, it sends this "451" code to tell your client to try again later.

​3 Steps to Handle the Microsoft 365 Outage

​While this is a server-side issue, there are steps you can take to bypass the local "Loading Loop" and ensure your data is safe:

  1. ​Check the Service Health Dashboard: Before troubleshooting, log in to the Microsoft 365 Service Health page. If you see "Service Degradation" for Exchange Online, then the issue is on Microsoft’s end and no local fix will work.
  2. ​Use "Outlook Web" Instead of the App: Many Tier 1 users report that while the desktop app shows the 451 error, the web version (https://www.google.com/search?q=outlook.office.com) is still functional. Clear your browser cache and try logging in via the web.
  3. ​Flush Your DNS: If you are stuck in a login loop, open Command Prompt as Administrator and type ipconfig /flushdns. This clears any outdated server routes that might be pointing to a dead node.

​Official Microsoft Update

​Microsoft is currently investigating the "Server-Side Edge" issues causing these temporary errors. They have stated that a fix is being rolled out globally. However, if you are a business user in the US, you may still experience intermittent connectivity for the next 12 hours as the DNS propagates.