[TAG] Nullmodem

[Rick Moen]

Quoting Kapil Hari Paranjape (kapil at imsc.res.in):

> Here is an alternative (which I probably learned from the LinuxMafia
> Knowledge Base) which I use:

Heh, what do _those_ guys know?  ;->

> 1. Setup a local MTA (aka sendmail alternative) using any simple to
>    configure MTA. Ensure that it is configured *not* to send mail
>    to the internet. This is so the system can send you messages if
>    it notices some configuration problems etc.

Reminds me of something that I used to be confused about:  I used to
mistakenly believe that you needed an MTA _daemon_ running in order to 
process purely-local mail such as system automated notices, logfile
analysis, etc.  It turns out you don't:  Just having any MTA able to run
as an on-demand mailer, only long enough to process the mail and then
terminate, is more than good enough.

On Debian, this program by default is Exim.  (On 2.2 "potato", it was
Exim3; in recent versions, it's the Exim4 rewrite-from-scratch series.)  

As is traditional on Unixes, this program is callable by the name
"sendmail", even though it's not actually the sendmail program at all:

  # ls -l $(which sendmail)
  lrwxrwxrwx 1 root root 5 2006-04-22 08:47 /usr/sbin/sendmail -> exim4
  #

Non-sendmail MTAs such as Exim3, Exim4, Postfix, and Courier-MTA all 
honour all of sendmail's command-line options as well.  Dan Bernstein's 
qmail of course honours only a subset of them, because this is the
easygoing Dan we all know and love.  ;->