On Wed, Sep 5, 2012 at 6:38 AM, Mark Andrews <ma...@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
