From the Tools menu, select Accounts, that brings up the Internet Accounts window.
(You may have to go to the Tools menu and choose Services, in that case choose Internet Email from the next window).

From the Internet Accounts window, click on the Add button and choose Mail, that brings up the Internet Connection Wizard.

Enter the Email Alias or Email/Reply-To Address from your Account Information

Click Next

Enter the following:
My incoming mail server is a POP3 server.
Incoming mail (POP3 or IMAP) server: pop.yourdomain.com
Outgoing Mail (SMTP) server: smtp.yourdomain.com

Click Next

Enter the following:
Account name:your E-Mail Account/POP Username from your Account Information
Password: your E-Mail Account/POP Password

Click Next

Click Finish

You're Done!