How do I 
  configure Netscape Navigator 3.x?
Please follow these steps:
1. Select Preferences... from the Edit pull-down menu.

2. Open the Mail & Groups section, and Click on 
Mail Server
 

3. Click on the Identity in left column.
 

All the other settings are optional. Choosing
Messenger Mailbox from the Communicator pull-down menu will open 
the part of Netscape that allows you to read and send mail.