Here is a quick guide to setting up your Darker IT Solutions Email Accounts using Mail for MAC in OS X 10.4, this method is similar to other versions of MAC Mail as well.
On the menu bar click Mail, then Preferences, then Accounts and finally click the plus at the bottom right.
Incoming Mail Server
Outgoing Mail Server
Outgoing Mail Server: mail.yourdomain
User Authentication – ticked
Username: your email address
Password: your mailbox password
Check your settings
Click Continue if you are happy with them.