MX handler that points to its own domain record?

[Ian Veach]

Greetings.  We have a bind9 server serving various campuses that do their
own IT.  One campus has a basic but unique set of needs:
	- they have a mail server.  for reasons not explained here,
	  it has always had an A record and no MX records.  they need
	  the A record tied direct to domain for the forseeable future.
	- they had the funds to buy just one mail processor (spam, etc),
	  and now want an MX handler, which is great.
	- BUT, they are worried about said handler failing, so would
	  like a (worse case) solution where the mail falls through
	  (unprocessed) to the mail server.
	- they are not sure if they can add another interface on to
	  their old mail server.  if so great, if not:

So, what they want is something like this (user at foo.bar.com):

foo.bar.com	IN A		10.10.10.1
		IN MX 10	handler.foo.bar.com
		IN MX 20	foo.bar.com

And my question is, is that OK?  The RFC seems to indicate that the MX RR
will be a host and therefore non-recursive - so it seems like that would
be ok, and would accomodate mail delivery for foo.bar.com even though
"handler" might be down.  But not sure, and not sure BIND implements this
way.  I'm recommending that they get a virtual interface on foo.bar.com
and use that as the second MX (e.g. IN MX 20 backupmail.foo.bar.com), but
they wanted to know if above would work.

Comments?

thanks!
imail AT nevada DOT edu