From the Window menu, choose Mail & Newsgroups. This will bring up Mail & Newsgroups, with the Account Wizard window on top. You will be presented with several screens.

Screen 1: New Account Setup

Email account: default
Click Next

Screen 2: Identity

Your Name: Your Name
Email Address: Your Email Address
Click Next

Screen 3: Server Information

Select the type of incoming you are using: POP
Incoming Server: yoursite.com
Outgoing Server: yoursite.com
Click Next

Screen 4: User Name

User Name: Your email address minus the @yoursite.com
Click Next

Screen 5: Account Name

Account Name: Your email address
Click Next
Click Finish

You will (once finished with the above) be presented with a Enter your password window. Enter the password for your account.

Note: The checkbox can be checked if you wish to use the Password Manager to remember it for you.

Congratulations, you've now setup Mozilla 1.x/Netscape 7.x to use your email account. Repeat the above steps to setup further email accounts.