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Re: draft-crocker-email-arch-03 Users, MDA and administrative domains

2005-03-07 22:54:46

At 11:12 PM 3/7/2005 -0500, Bruce Lilly wrote:

On Mon March 7 2005 19:27, David MacQuigg wrote:

> We need to treat a "Spam Bounce" as a separate kind of special message, to
> be handled differently than either DSNs or MDNs. We had great confusion in
> a recent discussion on [spf-discuss], because I was trying to define
> "Bounce" as something separate from DSN, but most think of the terms as
> synonymous.  So I'm not sure what to call it, but "Spam Bounce" seems
> reasonably descriptive and unambiguous.

Not either as far as I'm concerned.  Why don't you try to explain
what you mean by the term.

A Spam Bounce is a message generated in response to a spam, or what is suspected of being spam. This could be a reject message, or a challenge message, or a bounce generated by the recipient of the spam. In the past, these have been a problem, because they generally go to a forged address, where they become just more spam.

Email authentication will allow these Spam Bounces to be routed properly, back the path they came. If the email is *not* spam, the Spam Bounce will get back to where it belongs, most likely the same domain as the Return-Path. If it *is* spam, the Spam Bounce will be lost or ignored at the point where the spam was injected. All forwarders from the recipient back to that point, however, will have an opportunity to do something useful with the bounce (improve their blocking/filtering, etc.).

Here are the Actors in a spam scenario:

   +------------+                         +-----------+
   | Originator |                         | Recipient |
   +-----+------+                         +-----------+
         |                                      ^
         |                                      |
         V Sender    Return-Path       Receiver |
     +---------+    +--------+             +----+-----+
     |         |    | Notice |<------------+ Destin-  |
     | Source  +--->| Handler|     DSN     |  ation   |
     |         |    |        |<---+        |          |
     +----+----+    +--------+    |        +----------+
          |                       |             ^
          V                       |             |
     +---------+             +----+----+   +----+----+
     |Forwarder+-->  - -  -->|Forwarder+-->|Forwarder|
     +---------+             +----+----+   +----+----+
                                                ^
                         <-- Spam Bounce <--    |
            +---------+                    +---------+
            | Spammer +-->   - - - -    -->|Forwarder+
            +---------+                    +---------+

And here are the Agents:

                        +------+
             Originator | oMUA |<------------------------------+
                        +--+---+                               |
                           |    {smtp, submission              |
   Spammer                 V                                   |
       +------+         +------+                               |
       | MTA  |         | MSA  |<--------------------+         |
       +--+---+         +--+---+                     |         |
          |                |    {smtp                |         |
          |         Sender V                         |         |
          |             +------+                /+===+===+\    |
          .             | sMTA |                ||  dsn  ||    |
   Relays .      ^      +--+---+                \+=======+/    |
          .      |         |    {smtp              ^   ^       |
          | /+===+====+\   .                       |   |       |
          | || bounce ||   . Relays                |   |       |
          | \+========+/   .                       |   |       |
          V     <--        V                       |   |       |
       +------+         +------+                   |   |       |
       | MTA  |-------->| MTA  |                   |   |       |
       +------+         +--+---+                   |   |       |
       Relay               | Relay                 |   |       |
                           |                       |   |       |
                           |                       |   |       |
                  Receiver V                       |   |       |
                        +------+                   |   |   /+==+==+
                        | rMTA +-------------------+   |   || mdn ||
                        +--+---+                       |   \+=====+/
                           |    {local, smtp, lmtp     |       |
                           V                           |       |
                        +------+                       |       |
                        |      +-----------------------+       |
                        | MDA  |                               |
                        |      |<--------------------+         |
                        +-+--+-+                     |         |
                  local}  |  |                       |         |
                          V  |                       |         |
                    +------+ |                  /+===+===+\    |
                    | MS-1 | |                  || sieve ||    |
                    +-+--+-+ |                  \+=======+/    |
                      |  |   |  {pop, imap           ^         |
                      |  V   V                       |         |
                      | +------+                     |         |
                      | | MS-2 |                     |         |
                      | +--+---+                     |         |
                      |    |    {pop, imap, local    |         |
                      V    V                         |         |
                     +------+                        |         |
           Recipient | rMUA +------------------------+---------+
                     +------+

If the formatting is messed up on these figures, you can view the original at http://purl.oclc.org/net/edatools/email Spam Flows.txt

-- Dave

*************************************************************     *
* David MacQuigg, PhD              * email:  dmq'at'gci-net.com   *  *
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