Figures for [spf-discuss] Email Forwarder's Protocol ( EFP )
   -- David MacQuigg (Mon Feb 21 2005)
   -- subsequently modified, see date below each figure.
 
SpamFlows1 - Actors. Based on Fig.3 of draft-crocker-email-arch-03

   +------------+                         +-----------+
   | Originator |                         | Recipient |
   +-----+------+                         +-----------+
         |                                      ^
         |                                      |       
         V           Return-Path                |
     +---------+    +--------+             +----+-----+
     |         |    | Notice |<------------+          |
     | Sender  +--->| Handler|     DSN     | Receiver | 
     |         |    |        |<---+        |          |
     +----+----+    +--------+    |        +----------+
          |                       |             ^ 
          V                       |             |
     +---------+             +----+----+   +----+----+
     |Forwarder+-->  - -  -->|Forwarder+-->|Forwarder|
     +---------+             +----+----+   +----+----+
                                                ^
                         <-- Spam Bounce <--    |
            +---------+                    +---------+
            | Spammer +-->   - - - -    -->|Forwarder+
            +---------+                    +---------+
4/11/05


SpamFlows2 - Agents. Based on Fig.5 of draft-crocker-email-arch-03
adding Spammer and MTAs in middle, showing path of a Spam Bounce.
  -- draft-04 added "bounce" as synonymous with DSN.  We need to
     be careful to use the full term Spam Bounce when there might
     be confusion.

                        +------+
             Originator | oMUA |<------------------------------+
                        +--+---+                               |
                           |    {smtp, submission              |
     Spammer               V                                   |
       +------+         +------+                               |
       | MTA  |         | MSA  |<--------------------+         |
       +--+---+         +--+---+                     |         |
          |                |    {smtp                |         |
          |         Sender V                         |         |
          |             +------+                /+===+===+\    |
          .      ^      | sMTA |                ||  dsn  ||    |
          .      |      +--+---+                \+=======+/    |
          . /+===+====+\   |    {smtp              ^   ^       |
          | || spam   ||   .                       |   |       |
          | || bounce ||   . Forwarders            |   |       |
          | \+========+/   .                       |   |       |
          V     <--        V                       |   |       |
       +------+         +------+                   |   |       |
       | MTA  |-------->| fMTA |                   |   |       |
       +------+         +--+---+                   |   |       |
                           |                       |   |       |
                           |                       |   |       |
                           |                       |   |       |
                  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 +------------------------+---------+
                     +------+
4/11/05 


--- old figures ---

SpamFlows1a - Actors. (prior to changing Relays --> Forwarders)
Modified Fig.3 from draft-crocker-email-arch-03
 adding Spammer, DSN, Sender, Receiver, Return-Path, Bounce
 
   +------------+                         +-----------+
   | Originator |                         | Recipient |
   +-----+------+                         +-----------+
         |                                      ^
         |         Mail Handling Service        |
   /+=================================================+\
   ||    |                                      |     ||
   ||    |                                      |     ||
         V Sender      Return-Path     Receiver |
     +---------+    +--------+             +----+----+
     |         |    | Notice |<------------+         |
     | Source  +...>| Handler|             |  Dest   | 
     |         |    |        |<---+        |         |
     +----+----+    +--------+    |        +---------+
          |                       |DSN          ^ 
          V                       |             |
     +---------+             +----+----+   +----+----+
     |  Relay  +--> ..... -->|  Relay  +-->|  Relay  |
     +---------+             +----+----+   +----+----+
                                                ^
                              <-- Bounce <--    |
                   +---------+             +---------+
                   | Spammer +--> ..... -->|  Relay  +
                   +---------+             +---------+
2/28/05

Note:  The terms Source and Destination may be confused with the Source
and Destination Address, which is a much more firmly established
terminology {Internet Protocol, J.Postel,ed. RFC-791(STD-5),1981; TCP/IP
Illustrated, W.R.Stevens, 1994}.  These addresses are in the header of
every data packet, and they designate the source and destination on
each hop. i.e. every Relay in the above diagram is both a source and a
destination.  Likewise the term Relay may be confused in its role with
that of a Router.  Routers relay the packets from one station to the
next without changing the Source or Destination Addresses.  Relays, as
defined in draft-crocker, change these addresses.  For these reasons,
we will use the terms Sender, Forwarder, and Receiver in user-level
documentation, even though these terms also may be confused with other
uses.  If the meanings of these terms are not clear from context, they
should be stated clearly before they are used.


--- updated originals --

from draft-crocker-email-arch-04

Figure 3: MHS Actors
Bounce is now defined to mean *only* DSNs
We need a different term for Spam Bounce

+------------+                         +-----------+
| Originator |                         | Recipient |
+-----+------+                         +-----------+
      |                                      ^
      |         Mail Handling Service        |
/+=================================================+\
||    |                                      |     ||
||    |                                      |     ||
      V                                      |
  +---------+    +--------+             +----+----+
  |         |    |        |<------------+         |                
  | Source  +...>| Bounce |             |  Dest   |
  |         |    |        |<---+        |         |
  +----+----+    +--------+    |        +---------+
       |                       |             ^
       V                       |             |
  +---------+             +----+----+   +----+----+
  |  Relay  +-->.......-->|  Relay  +-->|  Relay  |
  +---------+             +----+----+   +---------+
                               |         
                               V
                          +---------+
                          | Gateway +-->...
                          +---------+
3/29/05

Figure 5: Protocols and Services
Added Disp and Bounces

                     +------+   +---------+
      ...............+ oMUA |...|  Disp   |<----------------+
      .              +--+---+   +---------+                 |
      .                 |    {smtp,                         |
      .                 V    {submission                    |
      .              +------+   +---------+                 |
      .              | MSA  |...| Bounces |< -----+         |
      .              +--+---+   +---------+       |         |
      .                 |                         |         |
      .                 V    {smtp                |         |
      .              +------+                /+===+===+\    |
      .              | MTA  |                ||  dsn  ||    |
/+==========+\       +--+---+                \+=======+/    |
|| MESSAGE  ||          .                       ^   ^       |
||----------||          .    {smtp              |   |       |
|| Envelope ||          .                       |   |       |
||  SMTP    ||          V                       |   |       |
||  RFC2822 ||       +------+                   |   |   /+==+==+\
|| Content  ||       | MTA  +-------------------+   |   || mdn ||
||  RFC2822 ||       +--+---+                       |   \+=====+/
||  MIME    ||          |    {local, smtp,          |       |
\+==========+/          V    {lmtp                  |       |
      .              +------+                       |       |
      .              |      +-----------------------+       |
      .              | MDA  |                               |
      .              |      |<--------------------+         |
      .              +-+--+-+                     |         |
      .        local}  |  |                       |         |
      .                V  |                       |         |
      .          +------+ |                  /+===+===+\    |
      .          | sMS  | |                  || sieve ||    |
      .          +-+--+-+ |                  \+=======+/    |
      .            |  |   |  {pop, imap           ^         |
      .            |  V   V                       |         |
      .            | +------+                     |         |
      .            | | uMS  |                     |         |
      .            | +--+---+                     |         |
      .            |    |    {pop, imap,          |         |
      .            V    V    {local               |         |
      .           +------+                        |         |
      .           |      +---- -------------------+         |
      ...........>| rMUA |                                  |
                  |      +----------------------------------+
                  +------+
3/29/05