Configure Exchange 2016/2019 to use a Smarthost

In order to route all outbound mail through MX Guardian, you must configure Exchange to use a smarthost. This guide will walk you through creating a new SMTP Connector and configuring it to route outbound mail to MX Guardian. 

Note: Make sure outbound filtering is enabled on your account before following this procedure.

1. Open Exchange Management Console.
2. In the left hand column select Mail Flow
3. Go to the Send Connectors tab
4. Click New to add a new send connector
5. Enter the name as 'MXGuardian', this is just a reference for the connection
6. Set the type to Internet
7. Click Next
8. Select Route mail through smart hosts
9. Click Add to add new smart host
10. Enter 'smtp.mxguardian.net' and click Save. 
11. You will now see the smart host listed. Click Next
12. Under 'Smart host authentication' choose ONE of the following options:
    1. Select None and then make sure your server's public IP address is listed on the Security page in MXGuardian under Trusted IPs
       - or -
    2. Select Offer basic authentication only after starting TLS and then enter your SMTP username and password which can be found on the Security page in MXGuardian.
13. Click Next
14. Click Add to add a new address space that is permitted to use the smart host
    1. Set the type to 'SMTP'
    2. Set FQDN to '*' meaning all domains
    3. Set cost to '1'
    4. Click Save
15. Click Add to add a permitted source server
    1. Click the appropriate server(s) from the list and click Add for each
    2. Click OK
16. Click Finish to save the connector
17. You may need to restart the Exchange SMTP / Transport services for the changes to take effect