Hi Pete,
--On Sunday, May 30, 2004 01:06:12 PM -0500 Pete Resnick
<presnick(_at_)qualcomm(_dot_)com> wrote:
1. How do we model the components and downstream interactions of srv1
and pc1:
|
MTA
|
+--<srv1>--+
| |
| messages |
| |
+----------+
|
<pc1>
pc1 does not retain any messages. Repeated readings of the same
message require repeated retrievals from srv1.
srv1 - MDA
messages - MS
pc1 - MUA
line between MTA and srv1 - SMTP
line between messages and pc1 - POP or IMAP or local access
This would make for an amazingly stupid POP client, a somewhat stupid
IMAP client, and a use of a local access client that would piss-off some
sys admins.
No! There is a well defined usage case for this: kiosk clients that do not
leave messages behind in a local cache. This is vital for any public access
email stations. Often people just get by with webmail in such cases but
there is no reason why a full blown desktop client can't offer the same and
thus provide the richer desktop GUI interaction with email over the limited
GUI a browser can provide.
2. How do we model the components and downstream interactions of srv2
and pc2:
|
MTA
|
+--<srv1>--+
| |
| messages |
| |
+----------+
|
+--<pc1>---+
| |
| messages |
| |
+----------+
Messages are retained on pc1 and not on srv1.
srv1 - MDA
messages under srv1 - MS
pc1 - MUA
messages under pc1 - MUA's local cache of messages (same for /bin/mail
messages in ~/Mail, POP client's mailboxes, or IMAP client's cached data)
line between MTA and srv1 - SMTP
line between messages and pc1 - POP or IMAP or local access
These two implementations/configurations are not architecturally
different.
There is a third option: messages kept on both server and client with
synchronisation.
In fact this is what I call the 'three modes of IMAP':
Online mode: client has no local cache of data, always re-fetches messages
from the server. This effectively implements kiosk mode.
Offline mode: client does 'pop-over-imap' and pulls all messages down to
the client cache and deletes from the server. Whilst that is a viable use
of IMAP, its a pretty pointless one, and I don't know of any clients that
actually behave that way.
Disconnected mode: client maintains a cache of messages that are on the
server and synchronizes changes between the two. The client may really be
in a situation where it connects/disconnects from the network, or it may be
connected but uses the local cache to speed up the 'online mode' where
local caching is allowed.
--
Cyrus Daboo