I definitely understand on the .NET webmail... .NET can be a pain but it sure is worth it when we use it to develop apps for large scale deployments due to the automatic compilation and caching of the code so it doesn't have to execute the whole script EVERY TIME. That significanly reduces server load.
chris wrote:But isn't it possible with a single externally viewable (Internet) IP and 2 internal LAN IPs to have IIS receive all external port 80 traffic and by using host headers forward appropriate domains to AMS to deal with directly rather than needing 2 public IPs? I'm sure I've heard of people doing that.
As for using the single external IP address to host both AMS Webmail and IIS sites on the same port, it's not possible (to my knowledge... and if it is, it can't be simple). We actually tried that before when we were trying to consolidate IP address usage. It doesn't work.
What it boils down to is that your traffic coming from the internet on 1 IP address/port can only go to one place. You can't have 2 "active" services (meaning ones that both send and recieve data) listening to the same port or you get REALLY screwed up results. You can have 1 "active" service and x number of "passive" services (meaning one that actually serves data and another that, say, records logs and is pass-through) on the same port as far as I know.
My guess is that the reports you've heard of it working (which it might, sometimes - and not others) have it implemented like this... which is not a viable solution.
We use all Cisco equipment for our networks, so I assume we would have found an alternative if it were possible (as enterprise class equipment gives you MUCH more flexibility as far as advanced configurations, etc. go).
Another possibility (if an ugly URL doesn't matter) is that if you're running a Server version of Windows, just setup multiple IIS sites that contain the host headers for the domains you use and have them redirect to the domain/port number. This way, you can use 1 public IP for everything (although AMS and IIS would still be on different ports). This should preserve the host header for AMS and allow you to access Webmail without having the user actually type
http://webmail.mydomain.com:8000 in the address bar (as long as you have the IIS site setup with the host header webmail.mydomain.com.
That's how we did it for a while. Average users just freak out when the see the :8000 at the end of a URL, if you know what I mean.
Cheers!