Sorry for the incomplete documentation at this time.  Here is a quick
overview of how to install SquirrelMail.

1.  Make Apache (or whatever web server) happy with PHP4.

2.  Unarchive SquirrelMail in a subdirectory that is accessable by the
    web server.  EX: /home/httpd/html/squirrelmail-0.1

3.  Edit the config file, config/config.php

4.  Point your browser to the location you specified in step 2.
    In this example, it's:  http://YOURHOST/squirrelmail-0.1/index.html