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MS vs. pop and imap

2004-05-29 11:32:33


CN> The architecture needs a "Message Store" piece.  The MDA delivers messages 
CN> the message store, while POP/IMAP transfer messages from the message store 
CN> the rMUA.

This looks like it needs to be discussed a bit. I think that reality is
a bit different than you describe.

Here's why:

POP really does finally delivery, "moving" messages from upstream to
downstream -- to choose some neutral terms. By contrast, IMAP does
"copying" from upstream to downstream. That is, POP changes where the
message actually resides. It is eliminated from the upstream. As a core
construct, IMAP leaves the message on the upstream host and simply
provides a copy to the MUA.

Each protocol can do some/all of the functions of the other.  But each
has the primary job I've described.  I think that that should be
depicted differentially.

Here's an attempt:

           |        MTA
           |         |  smtp, lmtp
           |        MDA   <-------------------------+
           |         |  smtp, pop, (local)          |
           |         MS                           sieve
           |         |  imap, (local)               |
           |         |                              |
           +------> MUA recipient (rMUA) -----------+

This might suggest that one could use pop to do final delivery and then
imap for access, but I think that showing more differential components
and "paths" in the architecture slide would be worse.

That is:

           |        MTA
           |         |  smtp, lmtp
           |        MDA   <------------------------------+
           |         |                                   |
           |         +---------------------+           sieve
           |         |  smtp               |  pop        |
           |         MS                    MS            |
           |         |  imap, (local)      |  (local)    |
           |         |                     |             |
           |         +---------------------+             |
           |         |                                   |
           +------> MUA recipient (rMUA) ----------------+

strikes me as too much about implementation and not enough about


 Dave Crocker <mailto:dcrocker(_at_)brandenburg(_dot_)com>
 Brandenburg InternetWorking <>
 Sunnyvale, CA  USA <tel:+1.408.246.8253>, <fax:+1.866.358.5301>