Got it.
I have made a small perl script as a service that would only return
reject as a policy (that sould have rendered most of the mailing
impossibble), and postfix was still mailing happily. Since I have
recompiled Postfix from the source, it was out of the question the the
process was faulty, so the only option is that Postfix couldn't connect
to a local service.
It was the firewall. The FORWARD chain was set to drop all, and the rest
is history......
Thanks everyone for the extraordinary efforts.
