What is

What is SPF

SPF is a TXT record that starts with v=spf1. It lists the hosts allowed to send mail for the domain. Two records that both start with v=spf1 on the same name are a permerror.

example.com. IN TXT "v=spf1 ip4:192.0.2.1 -all"

Evaluation that uses more than 10 DNS-querying terms returns permerror. Those terms are include, a, mx, ptr, exists, and redirect. all, ip4, ip6, and exp do not count toward the 10.