I got a postfwd daemon running and it does a great job.
smtpd_recipient_restrictions = [...] check_policy_service inet:192.168.10.7:10040
But if this server (192.168.10.7) isn't reachable, postfix rejects all mails with server configuration errors (4**). I am looking for something like a timeout. A timeout which skips this check if the policyd isnt running. I searched the documentation a lot, but there is nothing related to my problem.