SPF

SPF (Sender Policy Framework) is format and protocol used to reduce email spam. It helps an email server determine whether an email it receives has a forged sender address.

Format
An SPF record is a short string of text that begins with " ". It is normally placed in a DNS "TXT" record.

Specifications

 * RFC 4408
 * http://www.openspf.org/Specifications

Links

 * SPF Project Overview
 * Wikipedia article