Re: Dealing with s-p-a-m "backscatter"

[Russell Fulton <r.fulton () AUCKLAND AC NZ>]

Ian McDonald wrote:
> > > Has anyone come up with a more creative way to block the spam
> > > backscatter while allowing the legit non-delivery SMTP notifications to
> > > come through?
>
>
> MailScanner can add a watermark to each outgoing message (derived from a
> secret you configure), so that they appear in legitimate notifications.
> It can hence bin non-legit ones inbound :) .
>
> http://www.mailscanner.info/MailScanner.conf.index.html#Add%20Watermark
>
> I presume similar functionality is available in other packages, but I
> noticed it in MailScanner.
It would be difficult to retrofit I suspect.  The idea is straight
forward enough -- add an X-watermark header that is an MD5 of the
message id concatenated with a secret, then check for it in the headers
of returned mail and dump the bounce if a/ it is missing or b/ it does
not match.

Hmmm.... given that this is automated spam we are talking about simply
dropping bounces of messages that don't have the right format of message
id may work...  any one looked at doing that in either postfix or sendmail.

Russell