Click 'Mail,' and select 'Preferences'
 Click on the ‘Accounts’ tab, then click on the ‘+’ sign which is located at the bottom-left of the window, to add the new account
 Enter 'mail.domainname’ in the 'Incoming Mail Server:' field
 Enter your username (including '@domainname') in the 'User Name:'
 Enter your password in the 'Password:' field
 Select 'Add Server' from the pop-up menu labeled 'Outgoing Mail Server’, and enter 'mail.domainname’ in the 'Outgoing Mail Server:' field
 Enter '587' or ’25; in the 'Server port' field
 Un-check the box next to 'Use Secure Sockets Layer (SSL)’ if it is checked
 Select 'Password' next to 'Authentication:' and enter your username (including'@domainname') and password
 Click 'OK'