ietf-smtp
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Re: MS vs. pop and imap

2004-05-29 16:49:15

Hi Dave,

--On Saturday, May 29, 2004 11:32:29 AM -0700 Dave Crocker <dhc(_at_)dcrocker(_dot_)net> wrote:

Here's an attempt:

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

I think the following would be better (given comments by others with which I mostly agree):

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

Some things to note:

- imap can be used to deliver messages into the message store (the MDA -> MS step) since it has the APPEND command. Indeed a number of tightly integrated systems have the MDA doing imap appends linked with the sieve fileinto command to store messages into specific mailboxes beyond just the inbox. pop cannot be used in the same way as there is no equivalent to the append command.

- some clients 'pull' messages into their local store via smtp and ETRN, bypassing the message store. This is not very common but I do know of several ISPs that behave that way.

- I'm afraid we cannot ignore webmail, so note the addition of http as an MS->MUA access protocol. I guess http should appear for the sender MUA -> MSA step in which case the MSA is actually a webserver.

--
Cyrus Daboo