From: Ronald F. Guilmette (no email)
Date: Thu Nov 01 2001 - 03:29:35 EST
In message <>, you wrote:
>> Notice that I'm only talking about doing _forward_ DNS lookups (for either
>> `A' records or else `MX' records) on the original domain name and on all
>> ``trimmed'' versions of it, down to the second-level domain name. (No need
>> to go any further with the ``trimming'' than that.)
>
>NO! NO TRIMMING! That's what's bogus!...
I agree that it _should't_ be necessary, but if you are trying to bend
over backwards to avoid false positives, then you will use the ``trimming''
of domain names that I described, also, as part of your validation of the
HELO/EHLO name.
I wish I had a dollar for every mail server I had ever seem whose HELO name
was something like:
mail.jakes-pizza-planet.com
and where that domain name has -ZERO- `A' records (i.e. doesn't resolve
at all) but where if you look up the MX records for just
jakes-pizza-planet.com
you'll get something like:
exchange.jakes-pizza-planet.com
and that name _will_ resolve, and it will resolve properly to the IP of
the server in question.
There's no reason not to go the extra mile to be lenient about these kinds
of cases. You aren't going to get more spam if you are a bit forgiving of
these cases, but you WILL lower your false positive rate a bit.
You _did_ want to get your legit non-spam mail from Jake's Pizza Planet,
didn't you??
:-)
P.S. Of course all of this stuff flies out the window in the case of Hotmail,
because of their f**ked up HELO strings.
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