[Mimedefang] Soliciting opinions on filtering based on bad MXrecords

[Michael Sims]

mimedefang-admin at lists.roaringpenguin.com wrote:
> A lot of spam has MX
> records of currently reserved IP addresses that dont route (1.1.1.1
> shows up a lot).

Yeah, I don't believe my code snippet will catch '1.1.1.1'...  I'm just not
enough of an IP expert to know all of the addresses that are non routable.

>> (1) Retrieve the MX record for the sender domain.  If it doesn't
>> exist, I retrieve all A records for the sender domain.  If they
>> don't exist, I return false.  If they do, I test each A record,
>> returning true if any one of the records is "bogus", false otherwise.
>>
> Hmmm that might not scale very well for some silly sites that have 2
> or 3 Class B's on a fairly flat namespace. Unless I am
> misunderstanding what you are saying.

I think you are.  Here's an example:

MAIL FROM:<user at example.com>

First I try to get the MX record for "example.com".  If it doesn't exist,
then I query for the A record(s) for "example.com".  Usually there is only
one, although I have occasionally seen hosts having 2-3.  I'm not getting
all of the A records for the zone, I'm just getting them for the host
"example.com".

___________________________________________
Michael Sims
Project Analyst - Information Technology
Crye-Leike Realtors
Office: (901)758-5648  Pager: (901)769-3722
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