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Date:      Wed, 26 Aug 1998 01:32:09 +0000 (GMT)
From:      Terry Lambert <tlambert@primenet.com>
To:        nick.hibma@jrc.it
Cc:        matthew@netsol.net, hackers@FreeBSD.ORG
Subject:   Re: Imap4
Message-ID:  <199808260132.SAA29380@usr04.primenet.com>
In-Reply-To: <Pine.GSO.3.95q.980825094938.394d-100000@elect8> from "Nick Hibma" at Aug 25, 98 09:51:27 am

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>  > Can anyone tell me what imap4 is? i found it in 2.2.7 inetd.conf.
> 
> Mail server. It is built around the idea that you do not pull down all
> the mail to your system but keep it on the mail server. In that way you
> can read mail from several locations without logging in to various
> machines. It is also built with slow links in mind. So an IMAP
> connection is very useable on a 28k8 modem if you decide to just quickly
> browse the subjects. Sorting and deleting is all done on the server not
> on the client.

The wire protocol is similar to LISP: lots of silly parenthesis.

There is also the issue that it is impossible to implement an
IMAP client/server automaton using YACC/LEX and/or LALR parser
technology because of this (it wants stack-based parsing), without
providing a seperate start-state-stack, at a minimum (I have
created grammars for IMAP4 servers and clients, so I have some
experience here; not happy experience, but the code works...).

The primary idea is that the server stores the messages on behalf
of the client.  This allows for diskless/dataless clients, like
palm-pilots, digital cellular phones, JAVA-Phone's, and NC's, to
manage mail.

It also means that the client machine you use is less important
than your credentials, since it tracks against credentials.


Many ISPs dislike IMAP4 because it takes a lot of storage, and only
gives back increased modem usage and wire traffic in return for
the extra storage it consumes -- wait a minute, I get why they
don't like it... ;-).


One of the most annoying this is that, without a full IMSP implementation,
of which there is not one of, there is no provision for fanning out
envelope information into sub-mailboxes (which would make IMAP4
useful for virtual domain hosting, where POP3 fails to retain
envelope information because of a stupid agrument between Eric Allman
and Eric Raymond about "who is the MTA"), nor is there provision for
client specification of server side filtering rules (which would make
it otherwise more useful than POP3).

Basically, it's an interesting "also ran" that won't displace POP3
any time soon until its flaws are noted and corrected.

But it's a nice marketing bullet-item, if you're into that sort of
thing...


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.

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