From: Brent Kearney (brentkearneys.ca)
Date: Mon Oct 09 2006 - 17:28:24 CDT

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On Oct 9, 2006, at 15:29, Tim wrote:

>> Its purpose is to reject *all* mail from bogus MTAs - dialups,
>> misconifigured servers, MTAs that aren't registered in the
>> domains' DNS as
>> a "legal" MX, MTAs that don't reverse properly, etc., etc. If the
>> email is
>> forged in any way, it will never make it to DATA.
>
> That's great, except it makes the internet more expensive for the
> little
> guy. If you're trying to run a non-spamming personal mailserver
> off of
> a consumer DSL or cable line, you can get screwed by others' policies
> like this because you may not have control over your PTR records or
> how
> your ISP lists you as a non-MTA with other organizations.

Some university campuses maintain strict control over their reverse
DNS entries, and so departments or on-campus organizations, research
institutes, etc. that run their own mail servers will have non-
matching forward and reverse DNS entries on their MX hosts. Blocking
rules like this make life difficult for them as well.

Cases such as these raise the question, if the blocked mail never
gets into your network, how would you know about the rate of false-
positives?

Brent

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