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

[Stephen J. Turnbull]

Richard Stallman writes:

 > My proposal is that Emacs should check whether a bounce message
 > arrives in the local mailbox.  For this purpose, it doesn't matter
 > whether the human user thinks of looking in that local mailbox.

However, one case described earlier (which is a common case) is that
the bounce messages end up in root's mailbox (eg via the postmaster
alias).  In that case, Emacs won't be able to read the mail.

There are many other reasons why the bounces won't end up where the
user *can* find them, even if they (or Emacs) is looking for them.
They add up to a fairly high probability of failure to deliver,
assuming that the user has not configured their local MTA for Internet
mail, and only reads mail on another host.

This unreliability is unavoidable because mail is a store-and-forward
channel, lacking a mandatory mechanism for confirmation of receipt by
the addressee.  Neither the MTA nor the MUA can determine if the mail
has failed for quite a while (many days, in the case where the MTA
fails because the network connection is unavailable due to firewalling
and the like, and in the typical default configuration will keep
retrying in hopes that the link will come back up).

Of course there are many reasons to prefer mail for normal use by even
slightly experienced users.

But as Ted Z says, for the fallback channel, it's better to use a
direct connect protocol like HTTP, which can reliably give immediate
success or failure feedback.

Regards,
Steve