I believe linux distros still come with a mailserver (sendmail?), as well as a webserver (Apache), tons of free SW, and a worldwide community almost as good as BC.
You can run it on a junk machine that was going out in the trash (or that you found in the trash), just maximize memory and upgrade with a new HD (higher density means faster access and better data locality). I like the perpendicular recording head Seagates. An older (mainstream) machine is perfect for linux because the community has had time to develop the SW for the formerly cutting-edge proprietary HW. So you can save your Win2k3 license for something else. Clients can run Thunderbird.
I wish I had an excuse to maintain a linux server. I know the junk machine advice sounds crazy, but actually if you separate /usr, /home, /var, /tmp and such higher operational partitions from the lower level HW related stuff on / and /etc, you can decouple them and easily upgrade HW later. I used to have a poor man's laptop on a removeable hard drive that ran on separate machines, each with linux installed across a local boot partition / and the rest on my removeable. The plan failed when faster ATA protocols wouldn't work on the jerry-rigged printronix(?) connector on the HD caddy. Not a problem anymore with SATA cabling.
Edited by albert galick, 09 May 2009 - 09:13 AM.