Re: [Asrg] C/R Interworking Framework

Yakov Shafranovich <> Thu, 05 June 2003 02:54 UTC

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To: Vernon Schryver <>,, Eric Brunner-Williams in Portland Maine <>
From: Yakov Shafranovich <>
Subject: Re: [Asrg] C/R Interworking Framework
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Date: Wed, 04 Jun 2003 22:49:54 -0400

At 06:01 PM 6/4/2003 -0600, Vernon Schryver wrote:

> > From: Yakov Shafranovich <>
> > ...
> > However, if we are defining an SMTP process for CRI protocols, can we use
> > the VRFY command as a part of an ESMTP extension?
>What about deployment and adoption rates?  Do you want it to work
>even with MTAs not running your new protocol?
>In other words, do you want it to work only in theory or to also have a
>glimmer of a hope of working in the real Internet within the next 20 years?

As I pointed out before in a posting to Eric Dean, my vision is a 
multi-stage CRI protocol. The basic protocol would use RFC 2822 headers and 
human-readable email, which would be compatible with current MTAs. As C/R 
systems become more common, they can negotiate to use the other parts of 
the protocol such as an ESMTP extension or MIME fields. An extension 
mechanism would be in place where the protocol can be extended to support 
things like PKI, hash cash, etc. The VRFY command would be part of that 
ESMTP extension which will be used by C/R systems that want to, and not 
used by existing MTAs. Existing MTAs will start off by supporting the basic 
protocol or if they want the other parts.

Additionally, deployment and adoption rates is something that should be 
considered in more detail (this would be something that Eric Brunner can 
help us with). According to D. J. Berstein's SMTP statistics 
(, the following breakdown of 
major MTAs was present on the Internet in 2001 (out of 958):

401/958 41.85%          UNIX Sendmail
176/958 18.37%          Windows Microsoft Exchange or IIS SMTP
167/958 17.43%  UNIX qmail
57/958  5.9%            Windows Ipswitch IMail

These four accounted for about 84% of all MTAs with the other MTAs were 1% 
or less. Of these, qmail and sendmail account for 59.28% of all MTAs, with 
the Windows ones accounting for the other 24.27%.

IF a CRI protocol is implemented and both qmail and sendmail support it, 
that would mean that a sizable majority of the Internet would support it. 
If Microsoft jumps in, that would increase the effect. The question 
remains, taking the impact of qmail and sendmail, and the propagation rates 
for admins installing the newest versions, how long would deployment take?


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