4.4.62 Mail sent to the wrong Office 365 region

[ekrem ersoy]

Hello,

i have one issue that outgoing mail to only one m365 domains. i chacked mail logs and i see that; Reason: 4.1.0 - Unknown address error ('451', ['4.4.62 Mail sent to the wrong Office 365 region

no change have been made on ironport and m365, m365 tenant have alot "accepted domain" but i see that issue on one domain, and that domain receive email from other sides.

regards

[Udupi Krishna.]

Whats the email domain to which these delivery failures are observed at the moment? Can you paste the output of hoststatus <domain name> from the ESA where this error popped up. 

Has this worked before or anything that changed recently after which you started seeing this problem.

While this looks more like a Microsoft problem, feel free to look at - https://docs.microsoft.com/en-US/exchange/troubleshoot/email-delivery/wrong-office-365-region-exo