On Mon, Jun 28, 2010 at 17:34:38 +0800,
Ed Greshko <Ed.Greshko(a)greshko.com> wrote:
AFAIK, SPF records are queried by the receiving based on the domainname
in the "From" address. So, if a spammer is pretending to be sending
from user(a)hotmail.com the receiving end will make a DNS request for the
TXT records of
hotmail.com to determine its SPF records and how to treat
the email after the analysis.
SPF refers to the envelope sender address. That's why it causes problems
with forwarding. Normally the address in the from header matches the
envelope sender address, but that isn't always the case (mailing lists
being a big exception).