Patrick, thanks for your reply, but this is not 100% the answer I'm searching. I do not search for further mechanism to restrict incoming or outgoing mails. I'm searching for a mechanism to redirect mails that are send to an unknown recipient to a defined account. Anyway, thanks for your answer. Achim
smtpd_client_restrictions =
smtpd_client_restrictions = reject_rbl_client dnsbl.njabl.org, reject_rbl_client cbl.abuseat.org, reject_rbl_client blackholes.mail-abuse.org, reject_rbl_client sbl.spamhaus.org, reject_rbl_client bl.spamcop.net
smtpd_helo_required = no
smtpd_helo_required = yes
smtpd_sender_restrictions = hash:/etc/postfix/access
smtpd_sender_restrictions = hash:/etc/postfix/access, reject_unknown_sender_domain
warning: you may get an occasional valid post rejected usual disclaimer applies, ymmv