Blocking MX query

Wed Sep 5 01:48:37 UTC 2012

On Wed, Sep 5, 2012 at 6:38 AM, Mark Andrews <marka at isc.org> wrote:
>
>         MUA's can make MX queries to validate entered addresses
>         before SMTP/SUBMISSION is even attempted.
>

Sure but not on this guy's network as he's transparently proxying dns
and blocking MX requests on his proxy

Of course a bot can build up a rich cache of MX records from elsewhere
and send from a botted 3g modem connected host on his network