need advice on MTA and MDA

[Chris Yuzik]

Hi everyone,

We're getting a new server ready for deployment and it will be a shared 
"virtual domain" webserver/mailserver. Obviously will be running 
MailScanner et al. :-)

The hardware is a dual-Xeon 3 GHz machine with 4 x 400 GB hard disks in 
a RAID-5 array, 2 GB of ECC memory all in a 1U server. It's about as 
loud as a large hovercraft--fortunately it won't be living in our 
office. It's been torture-tested for the past couple of months here at 
our office and it's more than rock-solid stable. We've decided on Centos 
4.2, x86_64 edition for the OS. We're also going to be using Webmin and 
VirtualMin to make managing the virtual domains easier.

Here's where the advice request comes in:

Our old server that we're migrating /*from */runs Sendmail and Procmail. 
The new machine will be running _________ and _________.

What is the concensus as to what those blanks should be? Should I stick 
with Sendmail, or move over to Qmail? What about Procmail? Postfix?

Finally, our existing machine runs Squirrelmail and while it's very 
basic, it does the job. Any suggestions for a more robust webmail that's 
production ready?

Cheers.