Hi, there is XFORWARD command (http://www.postfix.org/XFORWARD_README.html) that smtpd and smtp can do.
It may be useful to prodvide XFORWARD data to external policy server (http://www.postfix.org/SMTPD_POLICY_README.html) via additional attributes to allow to implement MTA1->MTA2<->policy_server scenarios. Best, Deniss
