Mike, I think this is exactly what is going on. The domains that are having issues have greylisting on with the spam filtering service and are hosted on a farm of hosting servers. We have blocked port 25 on the main hosting IP of the web server, and moved the built in mail server to listen on another IP. This appears to be working, or at least has been for almost 12 hours. The real question is why is hotmail/live the only system that apparently does this; which seems to be in contradiction to RFC, and how everyone else does it. The one thing that MS chooses to be different with... Thanks, Carlos M. Perez Runcentral, LLC On 10/23/2012 4:28 AM, Michiel Klaver wrote:
Carlos,
check the mail logs of your web-server, your domain might have a primary A-record pointing to something different than MX-records. When the MX servers do something like greylisting and bounce with a temp-code (4xx) hotmail servers will try alternative records (like @ IN A) and might find a listening mail-daemon at your webserver.
At 23-10-2012 00:16, Carlos M. Perez wrote:
Hi,
We're trying to resolve some delivery issues reported by hotmail users. Started happening a few weeks ago. Getting immediate NDRs, and the server that is supposed to receive the email has no records of attempts. The messages also don't match what the receiving server should be sending. The server(s) listed in the MX should receive all email without authentication, since it's a mail filtering service (Maxmail)
= Reporting-MTA: dns;snt0-omc3-s27.snt0.hotmail.com Received-From-MTA: dns;SNT133-W53 Arrival-Date: Mon, 22 Oct 2012 14:09:49 -0700
Final-Recipient: rfc822;administrator@xxxx.com Action: failed Status: 5.5.0 Diagnostic-Code: smtp;550 authentication required =
Kindly contact me off-list.
Thanks,