From: Bill Stewart <bill.stewart@pobox.com>
Date: Fri, 20 Feb 1998 16:20:49 +0800
To: cypherpunks@Algebra.COM
Subject: Re: Dealing with Spam, Part 2
In-Reply-To: <2358.199802181427@cronus>
Message-ID: <3.0.5.32.19980220001517.008a6300@popd.ix.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain



At 02:27 PM 2/18/98 +0000, T.G.Griffiths@exeter.ac.uk wrote:

>Mark@unicorn.com makes a good point about MailGuard.
>If A and B both run MailGuard, and neither is on the
>other's allowed list, do you get an infinite bounce
>when A mails B or does the prog. get around it? I can
>think of a couple of ways, but what does MailGuard do?

The classic implementations of systems like that do
one of three things
0) Don't think, leading to infinite mailbounces
	(often caught in testing, since it's very bad.)
1) Prevent loops, but there's no way to communicate
2) Prevent loops, and recognize mail from other MailThingies,
	which makes it easy for Spammers to forge.

If you get fancy, you can probably work something like
	Receive message
	Send and record Alice-cookie ->
			<-- Reply with Alice-cookie and new Bob-cookie
	verify Alice-cookie and accept message
	Reply to Bob-cookie
			--> Verify Bob-cookie for future use

				Thanks! 
					Bill
Bill Stewart, bill.stewart@pobox.com
PGP Fingerprint D454 E202 CBC8 40BF  3C85 B884 0ABE 4639