Microsoft 365 ran into troubles on Thursday. The company issued an update on X even as services like Outlook, Microsoft Defender and Microsoft Purview were hit.

“We're investigating a potential issue impacting multiple Microsoft 365 services, including Outlook, Microsoft Defender and Microsoft Purview. Further information can be found in the admin center under MO1221364,” they said.
Meanwhile, Downdetector showed over 11,000 people facing problems with Outlook alone at the time of writing. Most of the complains were around being unable to receive messages.
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Many complained on the Downdetector page itself while some took to X to voice their troubles.
“I can't do other work because I can't get my 2-factor authentication email,” one person wrote, showing how intrinsically Microsoft services are linked to day-to-day work for many.
Meanwhile, two people shared the error message they were getting. One person wrote, “451+4.3.2+Temporary+server+error.+Please+try+again+later+ATTR2+.” Another added, “451 4.3.2 Temporary server error. Please try again later ATTR2.”
{{/usCountry}}Meanwhile, two people shared the error message they were getting. One person wrote, “451+4.3.2+Temporary+server+error.+Please+try+again+later+ATTR2+.” Another added, “451 4.3.2 Temporary server error. Please try again later ATTR2.”
{{/usCountry}}One person on X said ‘this is serious’, pointing to the ongoing outage. While an estimated time for services to be restored has not yet been given, here's some quick fixes one might try when faced with the ‘451 4.3.2 Temporary server error’.
How to fix 451 4.3.2 Temporary server error?
In case of a temporary server error, it can mean that the recipient's server is busy, overloaded, or undergoing maintenance. This might cause it to temporarily reject emails.
One way to get around this problem is to wait and try again later. Since it indicates problems on the server side, there isn't much individual users can do. They can check for Microsoft outages, which is the case now.
IT Administrators can verify server health, review DNS, run diagnostics, and check connectors to try and understand why the temporary server error is occurring. However, as it has been noted by Microsoft itself, there is some issue with Microsoft 365 which is impacting Outlook as well, and leading to the error message, meaning there is nothing on the user side that can be done for the issue.