Query: What to do if you use an A record but can't handle mail

Gentlemen -
        Apologies for intruding in this manner, but I have a query for which
the usual sources don't seem to have an answer.

What is the collective wisdom on providing A records (for Internet access) but
stopping mail access? There are a large number of machines here in University
College Dublin which require Internet access but can't run a SMTP server
(they're PC and the like). I want to ensure that anyone trying to send mail to
them gets a prompt refusal -- what I plan to do to is provide a DNS entry
like this:

        toaster.ucd.ie. IN      A       137.43.2.29
        toaster.ucd.ie. IN      MX      undeliverable.ucd.ie.

The host undeliverable.ucd.ie doesn't exist, which should as far as I know
return a prompt "can't deliver mail" message. So, is this how other people do
it? Is this the right way? Is there a better way? Any and all suggestions will
be gratefully received.


 - Arthur Green
   University College Dublin Computing Services
   Tel: +353 1 706 2456  Fax: +353 1 283 7077  E-mail: arthur at midir.ucd.ie