SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) are two methods to help indentify email which is likely not SPAM.  SPF was originally proposed in 2003 by Meng Weng Wong and Wayne Schlitt (SPFv1 RFC4408) as an open standard (SPF is backed by the Sender Policy Framework Council); DKIM originally merged and enhanced DomainKeys from Yahoo and Identified Internet Mail from Cisco (RFC4870 superseded by RFC4871) forming an open standard (DKIM is backed by an industry consortium).

Both SPF and DKIM attempt to provide information to receiving SMTP servers about whether or not a particular email message is authentic.

SPFv1 uses a very simple approach where a domain’s DNS server provides a root level TXT record that supplies information about SMTP mail servers that are permitted to originate domain email.

DKIM uses a more complex digital signature on each message (information about which is stored in a sub-domain in domains DNS containing self-signed keys).

You can read up on the specifics of each through the reference links provided below.

SPF (Wikipedia)

Microsoft SPF Record Wizard · OpenSPF Wizard

DKIM (Wikipedia)

Originally posted 2010-03-06 02:00:56.