Can somone help me understand how Postfix, IMAP and Squirrelmail interact? When IMAP is installed does it become it's own server or deamon? And does the install of IMAP effect the settings on Postfix MTA? What changes do I need to make to make a connection to Webmail?

I can get to the Squirrelmail log on screen from a web browser locally and from the internet, but I get the error-

SquirrelMail version 1.2.10
By the SquirrelMail Development Team
ERROR
There was an error contacting the mail server.
Contact your administrator for help.

I have installed:
RH7.3
PHP4
Apache
IMAP-Courior



Thanks for your help!

Vince