http://bugzilla.spamassassin.org/show_bug.cgi?id=3417





------- Additional Comments From [EMAIL PROTECTED]  2004-05-25 09:44 -------
Subject: Re:  New Rule: Checking sender IP against MX records From: [EMAIL 
PROTECTED]

On Tue, May 25, 2004 at 09:18:29AM -0700, [EMAIL PROTECTED] wrote:
> Hmmm, where can I read abount SPF?

http://spf.pobox.com/

> I think, DNS requests will be cached effectivly...

That's not my issue.  "MX" is meant to specify who receives mail for
given domain/host/etc.  It's now suggested to overload MX to also mean
who can send mail for give domain/host/etc.

Also, if I have several machines, all of which are allowed to send
mail for my domain, I have to add more 1 record per-domain.  Not only
is that asking for errors, it's also making the DNS response larger --
which could mean that it'll have to go TCP instead of UDP, which has a
huge impact on DNS performance.  With SPF, I only need to add 1 record
which allows them all.

> >> About 98% of spam flag on this test
> >> About 50% of ham flag off this test
> 
> No! It rule like AWL, like good whitelist - it very effective, may be we shold
> revert flag and assign score<0 (-1.6 for example)

I must be missing something...   If the rule hits on 98% of spam, but
also 50% of ham, the rule sucks.  It'll have an S/O ratio of somewhere
in the 0.6-0.7 range (assuming equal amounts of ham/spam).

> I think this rule will be in top20 best rules.

This isn't an anti-spam rule, it's an anti-joejobbing rule, so it's not
going to be in the top 20 anti-spam rules.

For instance, this rule would allow "bugzilla.spamassassin.org" to
send mail as "kluge.net" (it's a backup MX for my domain), whereas I
would consider that a forgery since it's not an outgoing mail server
for my domain.  With SPF I can clearly specify who I allow sending mail
using my domain.  The reverse is also true (kluge.net would be allowed
to send as bugzilla.spamassassin.org...)





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