[thelist] web-based email server

Hi,
I need to examine the options for YAHOO-like (smaller scale) web based
email server software. 
Right now, I'm looking into sake mail from endymion.com and edgemail.com,
and a few others.

But I'm gonna need some help on this one:
what things to look out for?
What would be the most important considerations in deciding which software
to choose?
What programs are the most popular ones out there?
Anyone good/bad experience with a particular program?

Thanks for your help! It's appreciated, as always!
Peter
Medellin
Colombia