Sender Policy Framework

Adoption Rate

Number of Domains

• Surveys conducted by The Measurement Factory on behalf of Infoblox in October 2008 and October 2009 indicate a ratio of .com and .net second-level domains with SPF records of 16.2% and 12.2%. (The 2009 survey is based on a smaller dataset but larger random subsample — go figure.)
• A continuous survey conducted by the WIDE Project observes .*.jp third-level domains and indicates an adoption rate of 39.5% in July 2010 (36.2% in August 2009, 24.5% in August 2008, 7.5% in October 2007, 3.5% in August 2006).
• Lars Eggert added SPF to his set of experimental deployment meters. At the moment his statistics covers only "top" Alexa sites for ten countries and the world, plus the domains used in e-mail addresses of current Internet-draft authors. On that somewhat limited basis, about half of these "top" domains publish some kind of SPF policy.
• spf-all.com counts domains publishing SPF "-all" policies. The statistics indicate that about 10% of all evaluated domains publish SPF policies. NEarly 99% of the published policies are syntactically okay, over 99.95% use no macros, and almost half of the SPF records end with -all. However 7 out of 10 -all policies are just that, "v=spf1 -all", indicating to be sending no mail at all.

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.

Miscellaneous

• Various Internet Drafts & RFCs reference RFC 4408.
• See also a Research page.