RE: NDR

  • From: <ChongJa@xxxxxxxxxxxxxxxx>
  • To: <exchangelist@xxxxxxxxxxxxx>
  • Date: Wed, 18 Jan 2006 13:51:27 -0500

Yes, we have 3 dedicated inbound mx servers and 2 dedicated outbound mx
servers. (Exchange routes to these (mailsweeper) smarthosts) All these
mx servers have reverse records. I guess my question is why does it
appear to be trying to resolve the internal DNS host name? If this was
the case many people would be screwed, as theres tons of environments
that utilize separate internal DNS namespace for AD. The header would
show the internal fqdn as the internal DNS for these scenarious but
lookups should not be performed on this. Also if you guys telnet to
their mail server and issue helo does it appear to work. Thanks for the
feedback.
 
ada.state.oh.us MX preference = 10, mail exchanger =
excelsior.odadas.state.oh.us

________________________________

From: Motlik, Richard [mailto:RMotlik@xxxxxxxxxxxxx] 
Sent: Wednesday, January 18, 2006 1:32 PM
To: [ExchangeList]
Subject: [exchangelist] RE: NDR


http://www.MSExchange.org/

Hello
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
Richard

________________________________

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


http://www.MSExchange.org/

I have a user that's getting an NDR when sending to a user
@ada.state.oh.us. 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
ada.state.oh.us in dnsstuff.com 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
(arcsmtp5.arcdmz.re.redcross.org) domain in the HELO command.
 
James Chong
ETS Sr. Exchange Engineer
Office: 703.206.7548
Cell: 703.863.1483
chongja@xxxxxxxxxxxxxxxx
 
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