How to Setup a cPanel & WHM Server as a Smarthost

Introduction

Many providers now block outbound connections on port 25, meaning that a cPanel system would need to configure a smarthost to allow outbound emails to function. This resource covers how to setup a smarthost using a second cPanel server on a different network.

Procedure

Please note that in the following instructions, "webserver" refers to the system on the network that blocks port 25, while "mailserver" refers to a second system through which email will be relayed.

Webserver configuration

1. In WHM, navigate to "Service Configuration » Exim Configuration Manager » Basic Editor."
2. On the "Mail" tab, set the "Smarthost support" value to * $mailserverip::587, replacing $mailserverip with the mailserver's IP address.
3. Click the "Save" button.

Mailserver configuration

1. In WHM, navigate to "Service Configuration » Exim Configuration Manager » Basic Editor."
2. On the "Access Lists" tab, set the "Trusted SMTP IP addresses" and "Backup MX hosts" values to $webserverip, replacing $webserverip with the mailserver's IP address.
3. Click the "Save" button.

DNS Settings

• MX records should point to the webserver's IP.
• SPF records should include the mailserver's IP.