Re: [Asrg] C/R Interworking Framework

Yakov Shafranovich <> Thu, 05 June 2003 15:02 UTC

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To: Dave Aronson <>, Peter Kay <>
From: Yakov Shafranovich <>
Subject: Re: [Asrg] C/R Interworking Framework
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Date: Thu, 05 Jun 2003 10:52:21 -0400

At 09:06 AM 6/5/2003 -0400, Dave Aronson wrote:

>"Peter Kay" <> wrote:
>  > 2. The recipient does not have me on their whitelist, so they send a
>  > challenge. But because their "FROM" address in the MAIL command is
>  > NOT the sender's address, TTK doesn't have that address on its
>  > whitelist so it sends a challenge to the challenge.
>  >
>  > End result is that the TTK user never sees the recipients challenge
>  > and the recipient never gets the email.  So what ends up happening is
>  > the recipient has to go through their quarantine folder and pull out
>  > the email.  The TTK user never gets the email because the challenge
>  > was killed in the MAIL command.
>  >
>  > So, to me, C/R systems need to at least use their end-users email
>  > address on the MAIL  FROM address in the mail command.
>Using a Reply-To could throw a bit of a monkey-wrench into this.  Perhaps
>the protocol should specify sending to the Reply-To (if present), and if
>that verifies, then consider the From verified as well.
>Also, many people have Lots And Lots of addresses.  I can think of three
>addies offhand of mine that lots of people get email from, not counting
>the temporaries, and sometimes I forget to switch addies when sending to
>certain people.  Perhaps the protocol could also say, "I might also send
>you email later under the following addresses", and whitelist them too,
>possibly with the whole C/R process repeated for each.
>Something tells me there are problems with these ideas, but there's too
>much blood in my coffee stream to figure them out at the moment.  |-)

Careful perusal of the relevant RFCs shows that there are differences 
between these fields. Section 3.6.2 of RFC 2822, distinguishes between 
various "sender" fields:

o "The "From:" field specifies the author(s) of the message, that is, the 
mailbox(es) of the person(s) or system(s) responsible for the writing of 
the message."
o "The "Sender:" field specifies the mailbox of the agent responsible for 
the actual transmission of the message. "
o "When the "Reply-To:" field is present, it indicates the mailbox(es) to 
which the author of the message suggests that replies be sent."

The "FROM" field is the one that will get C/R checked, since that is the 
mailbox that sent the email. Additionally, the "MAIL FROM" addresses that 
is used in SMTP is not intended to this purpose, rather it indicates a 
mailbox to which errors should be sent to. It is perfectly legal and 
sometimes even recommended in RFC 2821 to use <> for the MAIL FROM.


Yakov Shafranovich / <>
SolidMatrix Research, a division of SolidMatrix Technologies, Inc.
"One who watches the wind will never sow, and one who keeps his eyes on
the clouds will never reap" (Ecclesiastes 11:4)

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