You are looking at the wrong side. http://www.dnsstuff.com/tools/lookup.ch?name=arcsmtp5.arcdmz.re.redcross.org &type=A Since there is no A record, there is no way to see if there is a PTR record for the corresponding IP address. John T eServices For You -----Original Message----- From: ChongJa@xxxxxxxxxxxxxxxx [mailto:ChongJa@xxxxxxxxxxxxxxxx] Sent: Wednesday, January 18, 2006 9:14 AM 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 ------------------------------------------------------ List Archives: http://www.webelists.com/cgi/lyris.pl?enter=exchangelist Exchange Newsletters: http://www.msexchange.org/pages/newsletter.asp ------------------------------------------------------ Visit TechGenix.com for more information about our other sites: http://www.techgenix.com ------------------------------------------------------ You are currently subscribed to this MSExchange.org Discussion List as: johnlist@xxxxxxxxxxxxxxxxxxx To unsubscribe visit http://www.webelists.com/cgi/lyris.pl?enter=exchangelist Report abuse to info@xxxxxxxxxxxxxx