I am looking to create a mail server with basic calandar and attachment capability. I have setup qmail before - once, but this just needs to be internal. I don't want it to connect to anything outside. Is there a simpler mail server I can implement?

The server box currently has RH9 on it, but Im not opposed to a change of flavor.

Thanks!

Postfix is fairly simple to setup and configure. I would recommend changing distros based on the fact that Redhat 9 is OLD.. at least move to Centos if you wish to stick with Redhat based for a server.

Setting up postfix on Debian should only take a couple hours at most with a Good how-to such as this one.. http://www.debian-administration.org/articles/364 You can actually stop when you reach the point it starts configuring amavisd-new if you aren't concerned about spam filtering.
Then don't forget to set the hostname properly.. http://www.cpqlinux.com/hostname.html

OpenGroupware.org makes for a nice web based calendar and task scheduler, as well as web based front end for email access.
http://opengroupware.org/


But whatever Distro you decide to use theres a how-to out there somewhere to make your life easier..
Check out http://www.howtoforge.com if you have a chance.. several mail how-to's for various distros.. a bot more complex than you are looking for though I think.