the following i got from this userlist and i tried to implement it without ful understanding
Existing primitives can do this already. The example stops mail from yahoo.com/hotmail.com unless it comes from specific systems. Wietse smtpd_sender_restrictions = check_sender_access hash:/etc/postfix/strict_sender_map smtpd_restriction_classes = strict_client_domain /etc/postfix/strict_sender_map: yahoo.com strict_client_domain reject hotmail.com strict_client_domain reject /etc/postfix/strict_client_map: yahoo.com OK hotmail.com OK friendly.com OK friendly.com is a host that sends/forwards legitimate mail with a hotmail etc. sender address. While we're improving, the following rules as posted would cause mail from hotmail etc. to be bounced when the DNS times out. This fixes it: do client hostname access control only when the name lookup produced a definite (exists / doesn't exist) result. strict_client_domain = reject_unknown_client check_client_access hash:/etc/postfix/strict_client_map reject unknown_client_reject_code = 554 Wietse after i incorporated this into my main.cf i started getting the following (to postmaster): mailer-dae...@relay1.xxx.xx (Mail Delivery System) Add Address to Contacts To: postmas...@xxx.xx (Postmaster) Date: 24/01/2009 04:38 PM Subject: Postfix SMTP server: errors from d60-143.icpnet.pl[77.65.60.143] Transcript of session follows. Out: 220 relay1.xxx.xx ESMTP Postfix In: HELO d60-143.icpnet.pl Out: 250 relay1.xxx.xx In: MAIL FROM:<mi...@advpayroll.com> Out: 250 2.1.0 Ok In: RCPT TO:<bi...@xxx.xx> Out: 451 4.3.5 Server configuration error Session aborted, reason: lost connection i get several messages like this; what can be this?