> Sender Policy Framework (SPF) is a simple email-validation system designed to detect email spoofing by providing a mechanism to allow receiving mail exchangers to check that incoming mail from a domain comes from a host authorized by that domain's administrators. The list of authorized sending hosts for a domain is published in the Domain Name System (DNS) records for that domain in the form of a specially formatted TXT record. Email spam and phishing often use forged "from" addresses, so publishing and checking SPF records can be considered anti-spam techniques.
To add a SPF record in your DNS, insert the following line in your DNS zone:
After verification, you _might_ want to change your SPF record to `v=spf1 mx -all` so as to enforce the _HardFail_ policy. See https://www.spf-record.com/syntax for more details about SPF policies.
For whitelisting a IP-Address from the SPF test, you can create a config file (see [policyd-spf.conf](http://www.linuxcertif.com/man/5/policyd-spf.conf/)) and mount that file into `/etc/postfix-policyd-spf-python/policyd-spf.conf`.