Re: AT&T SMTP Admin contact?

[William Herrin <herrin-nanog () dirtside com>]

On Thu, Dec 3, 2009 at 1:25 AM, Chris Owen <owenc () hubris net> wrote:
> On Dec 2, 2009, at 9:52 PM, Valdis.Kletnieks () vt edu wrote:
>
> > It only stops forgery if the SPF record has a -all in it (as hubris.net does).
> > However, a lot of domains (mine included) have a ~all instead.
>
> I guess I've never really seen the point of publishing a SPF record if it
> ends in ~all.  What are people supposed to do with that info?
>
> Spamassassin assigns it a score of 0.6 but that is low enough it
> really doesn't have much since it doesn't assign any negative
> points for SPF_PASS.

Chris,

In addition to pushing the spam assassin score a little more towards
tagging it as a spam, I use SPF to suppress backscatter from my
confirmation system. When I receive a message whose spam probability
is ambiguous (spamassassin score between 3 and 8), I generate a
confirmation request to the sender. This allows the sender to put the
message in front of me anyway if it turns out to have been a false
positive, as it occasionally does.

If you publish SPF records (even with ~all) and the source doesn't
match, I won't generate that request. You've given me sufficient
forward knowledge to detect the forgery so that I can silently drop
the spam and still comply with RFC 2821's "must."

Regards,
Bill Herrin



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William D. Herrin ................ herrin () dirtside com  bill () herrin us
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