Re: ISP signatures on outgoing mail

["Mark M." <markm@voicenet.com>]

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On Thu, 3 Jul 1997, Ryan Anderson wrote:

> On Fri, 4 Jul 1997, ? the Platypus {aka David Formosa} wrote:
> 
> > There is now meany patchers to avoid mail relaying like this.  Good ISP's
> > don't let mail to go from an outside site to anoughter outside site.
> > 
> > >  (identical to how the ISPs customers drop off mail)
> > 
> > No its diffrent ISP's customers move from the inside to the outside.
> 
> Well, with current technology, it's not too difficult to forge DNS
> entries, and I imagine you could forge enough entires to confuse a reverse
> DNS lookup.  But this is really a different issue and I think the most
> recent version of Bind fixes some of these problems..

It would be possible to configure sendmail to only deliver a message that
has an authorized host in the "MAIL FROM" and "RCPT TO" commands.  This
could possibly be defeated by forging DNS entries in the ISP's nameserver,
but that's more than most spammers would probably want to risk.

> 
> -----------------------------------------------------------------------
> Ryan Anderson - <Pug Majere>     "Who knows, even the horse might sing" 
> Wayne State University - CULMA   "May you live in interesting times.."
> randerso@ece.eng.wayne.edu                        Ohio = VYI of the USA 
> PGP Fingerprint - 7E 8E C6 54 96 AC D9 57  E4 F8 AE 9C 10 7E 78 C9
> -----------------------------------------------------------------------
> 
> 


Mark
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