How to add a smart host in Office 365 Exchange online

In order for outbound email from Microsoft Office 365 to be routed through a smart host, we need to create a new send connector in Office365 and point it to your smart host.
Create a new send connector in Office 365

1. Log in to the Office 365 Exchange Admin Center (EAC)
2. Select the Admin > Exchangemenu
3. Select the Mail Flow > Connectors menu. Then, select Create a new Connector
4. Set the mail flow scenario
   • Select Office 365 from the **From: **drop-down
   • Select Partner Organization from the **To: **drop-down
5. Select Next
6. Enter a name and description for the connector. You may also select the checkbox to make the connector active immediately
7. Select Next
8. Select the Only when email messages are sent to these domains option
   1. Select the plus (+) to add domains that should use this connector
   2. Enter a value of * (asterisk).This is a wildcard that will route all outbound emails through your smart host
9. Select Next
10. Select the Route email through these smart hosts option
11. Select the plus (+) to add your smart host:_domain-com._outbound1-na.mailanyone.net
12. Click the Save button
13. Select Next
14. Select the checkbox for Always use Transport Layer Security (TLS) to Secure the Connection (recommended)
15. Select Issued by a trusted certificate authority (CA) from the list
16. Select Next
17. Add an email address of a recipient for a domain external to your organization, and select Validate to test

Note: If you did not choose to turn the connector on in Step 6, validation of the connector will fail. If your validation results show that the connection was successful, but the email failed to send because "The domain of the recipient is not configured as part of connector" - this may be due to the connector being disabled. Try enabling the connector and re-attempting the validation.

16. Once Office365 has been successfully validated, select Save
17. Update your SPF record accordingly