Error message 5.7.51 TenantInboundAttribution

Error

5.7.51 TenantInboundAttribution; There is a partner connector configured that matched the message's recipient domain. The connector had either the RestrictDomainsToIPAddresses or RestrictDomainsToCertificate set.

Answer

The inbound Office 365 connector that accepted the email contains a security restriction that was not met and was therefore rejected.