Ignoring unqualified MX's ?

[Ralf Hildebrandt]

On Wed, Mar 22, 2000 at 10:08:45AM +0100, torben fjerdingstad wrote:

> Both places we use bind. I would like a bind solution, which
> simply discards the bogus MX information.
> 
> If it is not possible to make bind junk unqualified MX'es,
> I would be happy with a patch (or an explation of why bind
> must announce unqualified MX'es).
> 
> I think I have pointed out a security problem in bind.
> Am I wrong?

Normally you wouldn't accept or relay mail for a domain you are MX for --
just because it's in the DNS -- unless you specify
FEATURE(relay_based_on_MX) (for sendmail). 

Nevertheless this can lead to a DOS, since bounces are sent locally, and
since these cannot be delivered, you end up with double-bounces piling up in
the mailbox.

The solution would be to disallow "localhost" for MX records.