While we are on the subject of “SPF”:http://www.geekfun.com/archives/000613.html, I’ll mention a “Thunderbird SPF plugin”:https://addons.mozilla.org/extensions/moreinfo.php?application=thunderbird&category=Message%20Reading&numpg=10&id=345 that I’ve just installed. It’s a bit quirky in that you have to tell it by hand what DNS servers it should use for it to work reliably (otherwise I suspect it forwards reqests to a server running on the author’s server, not something I feel good about).
It’s interesting to see what domains support SPF and which do not.
“Reed College”:http://www.reed.edu has SPF records for their mailservers while the University of Washington appearantly does not.
Others that do: Entercom, Netflix.
The plugin claims that Hotmail and MSN don’t support SPF verification, even though, to my untrained eye, their nameservers seem to report an appropriate SPF record.
E-mail sent through mailing lists, and forwarded from other personal accounts also fails because of the extra mailserver hop.