Re: [Exim] Exim on a single-user system

dman wrote:

> On Mon, Dec 31, 2001 at 05:50:22PM -0500, Derek Broughton wrote:
> | dman wrote:
> |
> | > Here's the problem. A MUA should not be dealing with SMTP -- an MTA
> | > should. mutt (and, AFAIK, elm and pine) do not do SMTP at all.
> | > Instead they pipe the message to the system's MTA and let it take
> | > responsibility for delivering it.
> |
> | That hair needs an electron microscope to split. :-)
>
> :-).
>
> | I can't imagine any good reason why an MUA shouldn't deal with SMTP.
>
> Do you consider exim to be a trivial program? Proper mail delivery is


But we're not talking about exim, and what an MTA has to do. We're
talking about an MUA handing off mail to either a program - like
sendmail or exim - or to a socket (the SMTP port). In either case, the
work done by the MUA will be the same (give or take a few lines). The
MUA has no need to be aware of most of the functions _permissible_ to
SMTP. It just needs to pass the message in accordance with the rules of
SMTP.


> not simple on the internet because it is such a large network. It
> also adds complexity to the MUA, reimplementing the same thing the MTA
> already implements.


Perhaps, but no matter what you'd like to be the state of the world, the
majority of MUAs are running on Windows and MUST deliver via SMTP.
THough I'd argue that it could _decrease_ complexity.

>
> Why not? They have to get on to your machine in the first place (so
> either they are legit or they are a cracker and you have bigger
> problems). For incoming SMTP connections, exim must verify the
> legitimacy of the message however from a pipe, the message is
> obviously legit since it originates from a user on the system.


But the SMTP daemon always needs to verify the legitimacy of a
connection anyway, there's no reason that it has to do any more work
when the other end is an MUA than when it's another MTA (though I could
buy an argument that it could be adding an intolerable amount of
overhead to a busy system).


> I've seen (or heard
> of) many MUAs that try to implement everything for themself (POP,
> IMAP, SMTP, etc) and are often buggy.

I've never tried using an MUA that 'implements' any of them. They just
talk to programs that implement the protocol. I can't really see how
you would have an MUA that runs on Windows that couldn't talk either POP
or IMAP, and as long as I'm going to have to use Windows for my clients
(which will be the rest of my career...), I plan to use an MUA that
talks IMAP and SMTP - and runs on both Windows and Linux (currently I'm
using Mozilla).

Consider your argument that letting the MUA talk SMTP, etc, increases
complexity. I know of a number of Unix mailers that provide specific
support for mbox and MH mail formats (not Maildir, more's the pity, in
any GUI mailers I've tried). If instead, you use a POP or IMAP daemon,
the mailer only needs to talk the one protocol, forget supporting
multiple mailbox formats.

(btw, it's a darn good thing mozilla talks SMTP - so that I can skip
straight through to my smarthost - because I'm having a hard time
getting exim to accept my outbound messages right now. I wish I could
figure out what I've screwed up :-) ).

derek