>My question is, will there be any implications "Out_There" of suddenly
>having a new IP and hostname for our mailserver, assuming we make the
>appro DNS changes?
Maybe you could arrange it on your router via port forwarding? You set it
up to forward all conenction for ports 25 i 110 to first machine. set up
the secod to monitor the first one and in an event of failure, dynamicaly
reconfigure port forwarding on your router to point to the second machine.
later on , when your first machine is up and running you can manualy revert
your router to the previous state (or even make it automatic too). Hope
you've got what i mean (sorry for bad english).
Kris