spf

SPF - Sender Policy Framework

What is it?

Sender Policy Framework. Anti-spam technique based on verifying the source of an email.

How does it work?

You create a list of all the mail servers that are allowed to send mail for your domain, and add it as a dns txt record. For example:

 gmx.net.        300   IN   TXT   "v=spf1 ip4:213.165.64.0/23 -all"