I haven't done a systematic check, but it seems that within days of
publishing SPF records, *attempts* at joe jobs against those domains
have stopped.
For example, for one site I manage, we would regularly get spam which
forged our own domain. Since an SPF record for the domain, the number
seems to have dropped off.
And since employing SPF filtering (yesterday) there have only been two.
I'm sorry that I don't have numbers to back this up. I haven't been
specifically tracking this, but will see if I grep anything useful of
out logs.
But if this isn't just my imagination, I am very surprised by the speed
of the spammers' response. The only way I think this could be done is
if the spamware itself is checking SPF records.
-j
--
Jeffrey Goldberg
Jeffrey(_at_)goldmark(_dot_)org http://www.goldmark.org/jeff/