This is an old revision of the document!
Configure proper mail delivery
SPF
SPF Engine is a nice little Python package to check SPF validity inbound to your Postfix server.
First of all install it:
emerge -vp mail-filter/spf-engine
Then link it to Postfix in main.cf:
smtpd_recipient_restrictions = $smtpd_recipient_restrictions check_policy_service unix:private/policy-spf
While in master.cf>
policy-spf unix - n n - - spawn
user=nobody argv=/usr/bin/policyd-spf