It may seem like a minor thing to some people, but the default webmail redirect on linux accounts is http://<YOUR_DOMAIN>.com/webmail .
Some people prefer or insist on using http://mail.<YOUR_DOMAIN>.com/ . This article will describe how to set that up.
Start by logging into your cPanel.
The first step from there is to delete the current DNS entry for mail.domain.com. You can do this through the Advanced DNS Editor: Learn More