Sender Policy Framework

Adoption Rate

Number of Domains

• Surveys conducted by The Measurement Factory on behalf of Infoblox in August 2006 and October 2007 indicate a rise in the portion of .com and .net second-level domains with SPF records from 5.0% to 12.6% within that time span.
• A continuous survey conducted by the WIDE Project observes .*.jp third-level domains and indicates an adoption rate of 16.3% in December 2007 (7.5% in October 2007, 3.5% in August 2006).
• Lars Eggert added SPF to his set of experimental deployment meters. Numbers are obviously biased due to the low and little representative sample size.

Mail Volume

• At the 2007 FTC Spam Summit, Microsoft reported 45% of non-spam received by their Hotmail service to be covered by "Sender ID", which essentially means mostly "v=spf1" records, plus possibly a few "spf2.0" ones.
• At the 2006 Conference on Email and Anti-Spam, Google reported about 20% of spam and 40% of non-spam received by Google Mail to be covered by SPF.

Anatomy of SPF Policies

• spf-all.com counts domains publishing SPF "-all" policies.

Miscellaneous

• Various Internet Drafts & RFCs reference SPF.