I'm not sure if this is the right area for the question, but here goes my first post!
I have a client that has been trying different linux based systems of and on to upgrade their existing mail server. The stats they would be running is 3 domains, 5000 users with around 2000 using the webmail interface and 3000 using pop3. Although the 'collaboration' features are nice they would not enable them. They are mainly looking at just MTA(spam and virus as well)/webmail. Currently they are using a qmail/mysql solution for their existing MTA and Atmail(buggy at best) for a webmail interface.
I've done some testing in house here with my clients data with the opensource version and with all services on a single Dell PE1950(4gb mem, duo core dual processor) and everything installs/setups/testing migrations with little to no hitch. Its a great product! But the memory utilization has me concerned. After a day or two I drop from 3Gb of free memory down to 1Gb. Only thing I'm doing is just internal testing, config changes and transferring mail with pop2imap/imapsync from their existing server to this server.
Reading the documentation a multi server environment sounds like just as much of a breeze as a single but with the clients needs and using similar Dell servers. How many boxes would be advisable. Currently the client does not have a SAN or any other shared storage nor do they want to take that large of a jump. But they wouldn't be opposed to go to a 2-6 server setup if its justifiable to gain additional growth, reliability and availability. Just curious as to what others have ran into with over 2k users.
Thanks in advance for bearing thru my long drawn out 1st post!