Backscatter & challenge response

Gerard gerard at
Sat Apr 12 12:08:36 IST 2008

On Fri, 11 Apr 2008 22:56:25 +0200
Hugo van der Kooij <hvdkooij at> wrote:

> Paul Houselander (SME) wrote:
> | In common with lots of people I've seen a massive increase in the
> amount of
> | backscatter my domains are getting. I implemented watermarking
> which has | helped a great deal.
> |
> | What I'm getting complaints about now are the mails coming in from
> annoying
> | challenge response systems, the mails don't come from postmaster, <>
> etc...
> | so the watermark does not get looked at.
> |
> | Just wondered if anyone had any bright ideals as to how to combat
> it? |
> | I've been looking at a selection I've been sent through this
> morning and | there doesn't seem to be anything consistent about them
> and there not | hitting many spamassasin rules.
> I considere them hostile spam senders and blacklist them accordingly.

I agree totally. I bounce any mail from a known 'challenge response'
user. The entire concept of 'challenge response' is flawed and a huge
waste of time and bandwidth.

gerard at

I believe a little incompatibility is the spice of life,
particularly if he has income and she is pattable.

	Ogden Nash
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