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AccuSpam wrote:
I am going to start a new thread, because IMHO this is too
important for SPF's success.
I am proposing that adding the option to specify the
probability that a message could be a forgery would:
"-all0.9993" which would mean 7 in 10,000 chance not a
forgery, 9993 in 10,000 chance is a forgery.
P(a @ b) = P(a) * P(b) / [P(a) * P(b) + (1 - P(a)) * (1 - P(b))]
The derivation is:
http://www.mathpages.com/home/kmath267.htm
Seems reasonable and well thought out. I have some things to add
(haven't read your citations in-depth)
FIRST: I'd suggest reversing the syntax - have the numbers be
replacements for the prefix. This allows for a simple extension of the
existing syntax.
Possible prefixes:
1(.0+)? - email from this chunk of the spf record is DEFINITELY
AUTHORIZED (PASS)
0(.0+)? - email from this chunk of the spf record is DEFINITELY
UNAUTHORIZED (FAIL)
0\.\d+ - email from this chunk of the spf record is POSSIBLY AUTHORIZED
(UNKNOWN)
So + is a synonym for 1, - is a synonym for 0, ~ is a synonym for 0.5,
and ? is a synonym for 0.1 (for some value of 0.1)
So you could have things like
v=spf2 1mx 1a 0.85include:partner.example.com 0.5ptr 0.15all
If the include recursively returned (say) a result of 0.75, that would
be multiplied by the 0.85.
SECOND:
The probability of spam-ness depends not only on where it comes from,
but where it goes. Perhaps macros could be developed to take into
account things like:
Does the email cross continental boundaries?
Does the email go from a .biz to a .com?
Is the recipient an organization which is well-known to the sender? Or
vice versa? (That is, does
sender-dot-example-dot-com.whitelist._spf.recipient.example.com exist?
With a probability tied to it between zero and one?)
Matthew(_dot_)van(_dot_)Eerde(_at_)hbinc(_dot_)com
805.964.4554 x902
Hispanic Business Inc./HireDiversity.com Software Engineer
perl -e"map{y/a-z/l-za-k/;print}shift" "Jjhi pcdiwtg Ptga wprztg,"
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