OCI: Unable to Relay email to External SMTP Server “Mail sent to the wrong Office 365 region”

Applies To:

Oracle Cloud Infrastructure - Version N/A and later 
Linux x86-64 

Symptoms 

Unable to relay emails to external domains using corporate SMTP server, whereas the emails to corporate domains deliver properly. 

 

Aug 19 06:13:17 <hostname> postfix/smtp[560628]: 22A30C01E252: to=<externaluser@externaldomain.com>, relay=corporatedomain.protection.outlook.com[x.x.x.x]:25, delay=0.68, delays=0.02/0/0.54/0.12, dsn=4.4.62, status=deferred (host coporatedomain.mail.protection.outlook.com[x.x.x.x] said: 451 4.4.62 Mail sent to the wrong Office 365 region. ATTR35. For more information please go to https://go.microsoft.com/fwlink/?linkid=865268 [ValidationStatus of '' is EmptyCertificate] [AM1PEPF000252DC.eurprd07.prod.outlook.com 2024-08-19T04:13:17.765Z 08DCBEA2CE65D9DC] (in reply to RCPT TO command))