Getting a new server

[Lisa Casey]

Hi,

My company (a medium sized ISP) has decided to replace one of our mail 
servers. We need more CPU power, memory, etc. My boss is talking about 
getting 2 good size hard drives with a raid card to mirror these. I was 
planning to install FreeBSD 5.3 (because that's the latest distro I have 
CD's for) unless anyone has a good reason why not.

I'll be installing Sendmail, mimedefang/spamassassin (somewhat CPU 
intensive), bind (for  a caching name server), Qpopper, procmail. We 
currently have 500 - 600 mail accounts on the current server, and plan to 
move these to the new server plus use the new one for growth (I don't know 
how quickly new mail accounts will be added, but say 20 to 50 accounts per 
month.

What would you folks reccomend as far as hardware goes? Hard drive size, CPU 
type,  amount of RAM, etc.?

Thanks for the input.

Lisa Casey