[Mimedefang] MX -> 127.0.0.1

[Les Mikesell]

On Mon, 2005-09-12 at 14:59, Matthew.van.Eerde at hbinc.com wrote:
> KAM wrote:
> > Thanks for the extra test cases.  Assuming they should all fail,
> > here's my new test stub.  Looks good to me.  Review and comment
> > appreciated. 
> > 
> > http://www.pccc.com/downloads/MIMEDefang/contrib/check_primary_mx_stub.pl
> 
> Review:
> 
> Why do we only care about the first?  I'm tempted to say, fail if ANY of
> the MX records is invalid.  Are there any broken configs out there that
> have multirecord MX's with only one of them (not the first) being 127.0.0.1?

Any MX of 127.0.0.1 is not only broken but malicious. However, I'd
expect it to be pretty common to have multiple MX's mixing public
and private targets on the assumption that inside hosts would hit
the working private number and outside hosts would fail and then
connect to the public address.  It's a bad assumption, since anyone
else might have a different server at that same private address, but
I'd still guess somebody does it.

-- 
   Les Mikesell
     les at futuresource.com