Postfix relay:

main.cf:

relay_domains = example.com, example2.com

smtpd_recipient_restrictions = …, reject_unauth_destination (recomandat)

pentru a defini unde se trimit mailurile de relay:

/etc/postfix/transport:

example.com smtp:mx.example.com

Links:
http://www.postfix.org/faq.html#backup

Postgrey (Greylisting) :

Se copiaza din arhiva de postfix din directorul examples/smtpd-policy scriptul greylist.pl in /usr/local/bin
Se editeaza greylist.pl:

$database_name=”/etc/postfix/greylist.db”;
$greylist_delay=60;

Nota: prima variabilal este fisierul unde se va pastra baza de date, iar a doua delay-ul in secunde dupa care se accepta mailul.
trebuie creat /etc/postfix/greylist.db si modificate permisiile astfel incat postfix sa poata citi si modifica acest fisier.

master.cf:

policy unix – n n – - spawn
user=nobody argv=/usr/bin/perl /usr/local/bin/greylist.pl -v

Nota: -v este pentru a fi verbose in loguri.

/etc/postfix/main.cf:

smtpd_recipient_restrictions =
reject_unlisted_recipient
…
reject_unauth_destination
check_sender_access hash:/etc/postfix/sender_access
check_policy_service unix:private/policy
…
policy_time_limit = 3600

Nota: in sender_access se pun domeniile considerate ca nu trimit spam si astfel vor sari de verificarea greylisting.
Trebuie creat acest fisier si dupa fiecare modificare rulat: postmap /etc/postfix/sender_access

Exemplu de fisier:
/etc/postfix/sender_access:
securityfocus.com OK

links:
How to kill 95%+ off your SPAM fast!
http://www.postfix.org/SMTPD_POLICY_README.html