pf on freebsd 6.1 on DMZ in m0n0wall question

[jan gestre]

hi to all,

i recently installed and configured
(postfix+dovecot+amavisd-new+clamav+dspam+roundcubemail) in my freebsd
6.1box, i placed the box in my dmz protected by m0n0wall, however i
have no
firewall on the mentioned box and i'm relying on m0n0wall to protect it. is
that ok? i'm new to freebsd and read about pf and i'm having some thoughts
of installing pf as firewall in my webmailserver but i'm afraid to mess
things up especially now that the box is already a production server, do i
really need to install a separate firewall? is it an overkill? if not then
anybody kind enough to lend a working pf configuration that allows http,
smtp and ssh, i've read the handbook but don't understand it much
particularly the firewall thing.

TIA