Advice for Internet facing Mailserver

[David Schulz]

Hello and good day,

i have setup a Server which is directly connected to the Internet,  
without NAT-Router or other Firewall Appliance. I am using FreeBSD  
6.2. I have pf enabled to only allow traffic on specified Ports. I am  
using Apache-13 + Postfix + Dovecot & mysql for my Mail-system. There  
is only one /home/User, which authenticates via a Key with Pass- 
phrase to sshd. The Mail-users all authenticate to a mysql database.   
I know that i could make use of chroot or better jail to secure the  
machine from possible exploits in postfix & co, but i am not yet  
comfortable with jail. Other then keeping my Ports (and system) up to  
date, can you give me some tips on how to secure my Box a little bit?

Thanks a lot,
David