postfix configuration

main.cf - spam reduction

# as by http://www.postfix.org/SMTPD_ACCESS_README.html

smtpd_delay_reject = yes
disable_vrfy_command = yes
smtpd_helo_required = yes

smtpd_client_restrictions =
 permit_mynetworks

smtpd_helo_restrictions =
 permit_mynetworks,
 permit_sasl_authenticated,
 reject_invalid_helo_hostname,
 reject_non_fqdn_helo_hostname,
 reject_unknown_helo_hostname
smtpd_sender_restrictions =
 reject_unknown_sender_domain

smtpd_relay_restrictions =
 permit_mynetworks,
 permit_sasl_authenticated,
 reject_unauth_destination

smtpd_recipient_restrictions =
 # send everything originating from localhost
 permit_mynetworks,
 # send everything logged in
 permit_sasl_authenticated,
 # reject_unauth_destination is not needed here if the mail relay policy is specified under smtpd_relay_restrictions (available with Postfix 2.10 and later).
 # highly trusworthy server, always allow
 permit_dnswl_client list.dnswl.org=127.0.[0..255].[3],
 # block everything where the sending ip is a known spammer
 reject_rbl_client zen.spamhaus.org,
 # block where the sending domain is a known spammer
 reject_rhsbl_sender dbl.spamhaus.org,
 # trustworthy server, allow if now blocked bs spamhaus
 permit_dnswl_client list.dnswl.org=127.0.[0..255].[2],
 # everything else goes through greylisting
 check_policy_service inet:127.0.0.1:10023