I'm no expert on Exchange ... Only the filtering in our service. It should be checked out. I'll see if I can wave the RFC under some noses...
Next week. Aloha, Michael. -- Sent from my Windows Phone ________________________________ From: Suresh Ramasubramanian<mailto:ops.li...@gmail.com> Sent: 2/27/2016 8:12 PM To: Michael Wise<mailto:michael.w...@microsoft.com> Cc: Franck Martin<mailto:fmar...@linkedin.com>; Mark Jeftovic<mailto:mar...@easydns.com>; mailop<mailto:mailop@mailop.org> Subject: Re: [mailop] proper NULL MX behaviour for MTAs? If there's an nxdomain for mx sendmail etc will fall back to the A - not to my knowledge if there's just a servfail No idea about exchange, you should be the expert on that, Mike --srs On 28-Feb-2016, at 9:39 AM, Michael Wise <michael.w...@microsoft.com<mailto:michael.w...@microsoft.com>> wrote: And Exchange. Aloha, Michael. -- Sent from my Windows Phone ________________________________ From: Franck Martin via mailop<mailto:mailop@mailop.org> Sent: 2/27/2016 7:39 PM To: Mark Jeftovic<mailto:mar...@easydns.com> Cc: Suresh Ramasubramanian<mailto:ops.li...@gmail.com>; mailop<mailto:mailop@mailop.org> Subject: Re: [mailop] proper NULL MX behaviour for MTAs? On Sat, Feb 27, 2016 at 7:23 PM, Mark Jeftovic <mar...@easydns.com<mailto:mar...@easydns.com>> wrote: On 2016-02-27 9:59 PM, Suresh Ramasubramanian wrote: > A domain with a null mx may well originate email but will absolutely not > receive email - so mail gets trashed at your end as well without staying > endlessly on your mall queues > > You can possibly correlate that mx with the behavior of domains that are > sending you mail.. Though a domain rather than IP bl may make sense. > Sorry, I realized after I sent that I needed to clarify that what I'm observing are MTAs attempting to deliver email to addresses at IP of the A record for the domain, ignoring the presence of its NULL MX. So the originating MTAs are ignoring the NULL MX and attempting to deliver to the A hostname, leading me to surmise they are spambots or zombies. This could be true but then RFC7505 is recent, so I'm not sure that proper MTAs are yet properly behaving. I wonder what sendmail, postfix, exim really do?
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