I've been asked to look into adding a mail server at a remote "branch office" (managing director's house). The only real requirement is that I do so without adding any more computers to the site. There is currently one machine running Smoothwall and one PC. The mail server can be anything that supports SMTP and either POP3 or IMAP. Because the PC is only on for about 12 hours a day it would not be appropriate to run the mail server. That leaves the Smoothwall box.
As I don't believe a firewall should be weakened by adding something like a mail server I'm considering whether to replace the existing Smoothwall box with one running Smoothwall and the mail server as virtual machines using VMware ESXi. Incidentally, I've never used bare metal virtualisation before. The plan would be to install 3 NICs. One for the Internet side, one for the LAN and one for ESXi itself, which would be connected to the LAN. The DMZ interface could presumably be handled by a virtual NIC.
Given that the machine would be located about 700KM away (as the crow flies) all management must be done remotely. Is this practical, bearing in mind that if the firewall goes down I would lose access to the host machine as well?
Edit: This mail server is to be completely independent of and in addition to the corporate mail system. I neither know nor understand all the reasons. Regardless, this is the task I've been given.