firewall + mail gw

[Carlos Alberto Pereira Gomes <carlos@gomes.cx>]

Hi,
I'm looking for suggestions about a small problem:

I've a home network connected to internet with an ADSL link, and with 4
users sharing two computers (windows machines). Each user has at least
two mail accounts in different providers.

I've already set up a linux firewall and it's running ok.

I'd like to set up some kind of email server (in the firewall machine) that 
collects all the emails for each user and let them read it with webmail or 
outlook from the internal network, and let me use some kind of
spam/virus filter.

What is the best combination of software that I should use to get this
solution?

Thanks,


-- 
Carlos