Forum Discussion
Hybrid Centralized Transport sending emails to EXO
I've discovered that Microsoft hosted tenants emails we receive is going directly to our EXO tenant and using the Hybrid Outbound connector going directly to on-prem Exchange by passing our on-prem E...
Properly configured, the sender should use MX records for mail routing. Some details are in this blog https://techcommunity.microsoft.com/blog/exchange/office-365-message-attribution/749143
You can create an inbound connector to reject any mail not from the correct location.
Regarding email processing by Exchange Online Protection (EOP), you cannot bypass this and emails will always be subjected to the threat protection policies. Microsoft recommendations for how to configure EXO/MDO when using a 3rd party service is outlined here https://learn.microsoft.com/en-us/exchange/mail-flow-best-practices/manage-mail-flow-using-third-party-cloud
A partner connector was created to reject all emails that doesn't match the hybrid certificate.
