Have a Linux email server and a Microsoft web server on the same machine

Is there a way to have a Linux email server and a Microsoft web server on the same machine?

Absolutely...I have a setup similar to that.
Use VmWare Server:
http://www.vmware.com/products/free_virtualization.html
It's free... It allows you to have 'virtual machines' which is great technology.

I have a server that I built and have Windows Server installed and it's hosting a website. I have a virtual machine that is running Linux. It's a machine in a machine.

The only thing to keep in mind is to get plenty of RAM. I wouldn't go under a Gig of RAM as a bare minimum.