[CentOS] setting up postfix

Does your postfix send emails directly or do you use a smarthost for
relaying? I'm asking because you're using a 10.x.y.z network
which means you use NAT for outgoing connections when delivering mails
directly to the destination server. Bad idea. Worse if the destination
server does some sanity checks (like spf or reverse checking of your
ip/dns etc).

Brgds

-- 
Freundliche Gruesse/Best Regards
Benjamin Hackl
IT/Administration

Media FOCUS Research Ges.m.b.H.
Maculangasse 8, 1220 Wien Austria
Tel: +43 1 258 97 01-295
b.hackl at focusmr.com