Since every cPanel server also handles mail for the domains on that server (unless you've set up a custom solution), WHM includes a number of tools that help you manage mail.
Click on the Exim Configuration Editor in the Server Configuration section of WHM to manage the settings of Exim. Exim is a Message Transfer Agent (MTA) that handles all incoming and outgoing mail as well as manages SMTP service.
On the main screen, you can set a few basic options or switch to the advanced configuration editor. The options you can enable or disable on this screen are:
Always set the sender: This feature is disabled ...