[K12OSN] Moving our email server

[mrok12osn at eastgranby.k12.ct.us]

In the near future, I am going to need to move our email server from one
ISP (Cox Cable) to another (CEN - Connecticut Education Network) and I
have never done this before.  Our email server is FC5 (postfix) built from
the K12LTSP CD's.

I'm wondering whether I can just put a second ethernet card in the email
server so both ISP's IP addresses (old and new) are active, update
iptables, and then notify the ISP that maintains our DNS pointers to
repoint to the new IP address.  Then after a couple of days, I can just
shutdown the old IP address.

Will this work?  Are there any issue with postfix?  Any help or
suggestions are appreciated.

Mark Orenstein
East Granby, CT School System