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Re: Changing the default for `send-mail-function'

From: Tim Cross
Subject: Re: Changing the default for `send-mail-function'
Date: Thu, 30 Jun 2011 10:13:36 +1000

On Wed, Jun 29, 2011 at 11:42 PM, Richard Riley <address@hidden> wrote:
> Lars Magne Ingebrigtsen <address@hidden> writes:
>> Richard Stallman <address@hidden> writes:
>>>     Times have moved on.  All other modern mail readers have moved on from
>>>     trying to use the local MTA to send email out, because the world has
>>>     changed.  These days, it's way more likely that you need to talk to your
>>>     ISPs local servers directly, and you need to fill out some credentials
>>>     tied to your account.
>>> If a client program can do that, why can't Exim do that?
>> Because SMTP is slowly moving towards a regime of per-user
>> authentication.
>> That is, to send someone email these days, you often have to provide a
>> user name and a password.  If you're the only one sending mail from your
>> machine, it's theoretically possible to configure exim to provide these
>> credentials to the upstream MTA.  (At least I think it's possible -- I
>> haven't actually checked.)  If there are two people sending email from
>> your machine, that obviously isn't what you want to do, what with the
>> password then being shared and stuff.
> Assuming I havent got completely lost here, exim4 "smart hosts" are a
> doddle to configure. But only for one user. For more than one email
> account/smtp smarthost there are a plethora of google hits some of which
> might work - matching email and/or user to the corect authentication
> details needed for that user/email specific smarthost. If thats not
> relevant excuse the intrusion.

I think this whole argument is still going around in circles and lots
of 'arguments are being put forward which appear to lack any real
facts or are theoretical musings about problems that may occur and are
not a good reflection of reality.

1. There are very few Linux distros that do not place their mail spool
in /var/mail. Those that I've seen have been deliberately configured
that way and it would be reasonable to assume that anyone who has
deliberately changed the default/standard settings has also configured
mail. However, testing for /var/mail is not sufficient to determine if
a local MTA has been configured/setup. I do believe there are tests
that could be done, but at best they would be heuristic in nature and
could not guarantee 100% accuracy. Whether they would be sufficient,
I'm not sure.

2. The whole multi-user, exim and smarthost thing is just a complete
misdirection and misunderstanding regarding mail server configuration.
You need an SMTP host to dispatch mail. That dispatching has nothing
to do with your mail address or your recipient address. If you have
multiple users on a system and provide an MTA on that system, that MTA
either has the necessary access to communicate with other mail servers
or it has sufficient authority to pass the mail onto another MTA for
dispatch (a smarthost).  If authentication is involved, it is only
involved at the local MTA. (it is theoretically possible for a local
MTA to be configured to relay mail to specific SMTP servers based on
the credentials of the sender, but in nearly 20 years of dealing with
mail servers, I've never ever seen this configuration).  The main
reason you don't have this sort of multiple smarthost configuration is
because the management overhead is too high compared to the benefits.
>From a client perspective, the SMTP server which dispatches the
message is largely irrelevant.

3. The majority of ISPs use IP address to control access to their SMTP
server for their clients connecting from within their network (i.e.
DSL, modem users) and only use authenticated SMTP when the client
wants to send mail from outside the network. However, it is common to
configure your mail to use authenticated SMTP even when on the ISPs
network simply because of convenience. Many people these days use
laptops and multiple networks. Having your default SMTP configuration
setup using authentication means you will be able to use your ISPs
SMTP server even when not on their network and avoids the need to
maintain multiple profiels and manage switching of profiles depending
on the network you are using.

The major 'issue' I can see with this proposed change of default is
the possible impact to users who use emacs, but don't use it as a MUA
and therefore don't configure it for sending mail, who may want
to/need to submit a bug report using the report-emacs-bug
functionality. Lars' proposed solution of initially prompting for the
necessary information may be sufficient to address this issue - we
will need to look at it ans see if it needs refinement or not etc. It
is also possible that perhaps using mail to automate (or
semi-automate) lodging of bugs needs to be reviewed?

What I'm still not clear about is why this decision to change the
default to smtpmail? I've seen references to arguments concerning the
world marching on and this being more in line with how other software
does it etc, but that seems a little weak to me - there are lots of
things that have not changed for the better, so the world moving on is
a poor argument without more explination and there are plenty of
things other software does which emacs does not do and is a
significant reason why I use emacs and not that other software. This
is not to say I disagree with the proposal, but rather that it is not
clear why the change is required/desired. A better understanding of
that might help provide better suggestions for solutions that work for
more people.


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