• From: "Motlik, Richard" <RMotlik@xxxxxxxxxxxxx>
  • To: "[ExchangeList]" <exchangelist@xxxxxxxxxxxxx>
  • Date: Wed, 18 Jan 2006 13:32:16 -0500

I had this problem the other day. Are you sending email on one path and
receiving email on another?? I had the situation where exchange was
sending email directly to the internet but we are receiving on an anti
spam box that sends to our firewall, the name does not resolve to the
sending IP address so consequently you get this reply. Hope this helps


From: ChongJa@xxxxxxxxxxxxxxxx [mailto:ChongJa@xxxxxxxxxxxxxxxx] 
Sent: Wednesday, January 18, 2006 12:14
To: [ExchangeList]
Subject: [exchangelist] NDR

I have a user that's getting an NDR when sending to a user Although the NDR appears that it's doing some sort of
reverse DNS lookup, I don't think this is the case. When I put in in it comes back with an error that their
mx record is referencing a cname rather than an A record. I did some
research which suggests that when this is any mail sent to this domain
is rejected. When I connect to their mail server on port 25 and issue a
helo it comes back with syntax error. When I issue ehlo it does not
appear to do anything. Wondering if this is something on their end or
ours. (All our outbound mail goes out to mailsweeper smarthosts (2)
Received:571 - MAIL REFUSED - Reverse DNS failed; cannot resolve the
( domain in the HELO command.
James Chong
ETS Sr. Exchange Engineer
Office: 703.206.7548
Cell: 703.863.1483
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