apt-get update && apt-get install postfix-policyd-spf-perl -y

vim /etc/postfix/master.cf

…
policy-spf  unix  --       n       n       --       --       spawn
user=nobody argv=/usr/bin/perl /usr/sbin/postfix-policyd-spf-perl
vim /etc/postfix/main.cf
…
smtpd_recipient_restrictions = permit_mynetworks,permit_sasl_authenticated,check_policy_service unix:private/policy-spf
…

Важно: check_policy_service да се намира непосредствено след permit_mynetworks