To add a domain: 

1. Log on to the HES console.
   • For Customer Licensing Portal (CLP) customers
     • Europe, Middle East, Africa (EMEA): Europe, Middle East, Africa (EMEA): https://tm.hes.trendmicro.eu
     • All other regions: https://tm.hes.trendmicro.com
   • For Licensing Management Portal (LMP) customers
     • EMEA: https://<tenant-id>.hes.trendmicro.eu
     • All other regions: https:/<tenant-id>.hes.trendmicro.com
   • For XSP customers
     • EMEA: https://ui.hes.trendmicro.eu
     • All other regions: https://ui.hes.trendmicro.com
2. On the HES console, go to Domains and click Add to add your managed domain.
3. Enter the following information:
   • Domain name
   • Number of seats that will be assigned to the domain
   • FQDN or IP address of inbound servers
   • Port number of your mail server
   • Email address for sending a test message within the domain

   

4. (Optional)Enable Outbound protection routes outbound email through HES. Select whether or not you are using O365, Google G Suite, or provide the IP address of the target outbound server.
5. Click Add Domain.
6. Click OK to confirm adding the managed domain.

The domain request will go into an "Adding" status.

A Welcome Email from HES Support will be sent to the address registered to the HES account. The domain status will remain in the “Adding” state until the inbound HES server address is added to the domain’s MX records. The MX record pointing to HES may be assigned the lowest priority to avoid interrupting the current mail flow. Once HES detects the MX record change, the domain will enter the “Activated” state.

At this point you may send a test email to check the mail functionality.

For more information, you may check this documentation on Configuring a Domain.