How to enable custom mail HELOs

Introduction

You may wish to have domains use custom mail HELOs instead of the system default. This article provides the steps to enable and add custom mail HELOs.

Procedure

1. Log into WHM as the 'root' user.
2. Navigate to "Home / Service Configuration / Exim Configuration Manager."
3. Under the "Basic Editor," click the "Domains and IPs" tab.
4. Disable the "Use the reverse DNS entry for the mail HELO/EHLO if available" option.
5. Enable the "Reference /etc/mailhelo for custom outgoing SMTP HELO" option.
6. Access the server's command line as the 'root' user via SSH or "Terminal" in WHM.
7. Open /etc/mailhelo in your preferred text editor.
8. Add the domains and mail HELOs you would like these domains to use with the domain.name: domain.helo format.

   example.com: example.com
   sub.example.com: example.com
   example.net: example.net
   addon.example.net: example.net
   *: hostname.example.com

   Please note that the last entry in the above example is a wildcard that represents every domain not explicitly listed. It is considered to be the default mail HELO.
9. Save the changes and exit the text editor.

Additional rescources

Exim Configuration Manager Basic Editor: Domains and IPs

How to Configure the Exim Outgoing IP Address