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NDR (Recipient unavailable error)

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7 replies

by technogal63

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We are having a problem with sending mail to one particular international address through our Exchange server. Mail sent via an internet mail service (such as Yahoo) goes thru with no problems at all. We are currently using Exchange 5.5, SP 4 on an NT 4.0 platform.

The NDR message we get is as follows:

"Your message did not reach some or all of the intended recipients.

Subject: Test from Mail Server
Sent: 4/11/01 3:33 PM

The following recipient(s) could not be reached:

'xxxx@xxx.pl' on 4/13/01 3:35 PM
The recipient was unavailable to take delivery of the message
The MTS-ID of the original message is: c=US;a= ;p=Interactive Serv;l=EXCHANGESERVE-010411203319Z-3837
MSEXCH:IMS:, Inc.:xxxxxx:EXCHANGESERVER 3499 (000B09AA) Host unreachable

Any idea what might be causing this problem? This seems to be the only address which generates this NDR and this is a critical business partner of ours! Any help would be greatly appreciated.....

7 replies

by mckaytech

This could be either a name resolution (DNS) problem or a firewall problem somewhere along the way. I would bet on the DNS problem.

First, I would try and ping their mailserver by name. If it doesn't resolve properly, you have a DNS problem that will have to be resolved (or you could use a HOSTS file entry as a temporary measure).

If it does resolve properly, I would then try to telnet to port 25 on their server. If that doesn't work, there is a firewall or filter somewhere along the path.

I've also seen a few times where a spam filter has caused this sort of problem when an ISP programs it to reject everything from a range of IP addresses that happens to include yours.

paul

by wzab1

It's also possible the recipient has receive limits on their email account. Receive limits could give you the message you're seeing even though their account is available. MS TechNet article #Q812557 references this. Also, TechNet article #Q246674covers the install & config MS Exchange Link Monitor. It's used to diagnose email message routing.

by cscript

I believe that the best way to troubleshoot this problem is to start by manually telneting to port 25 of that host.
Do an nslookup for their mx record. Is it the same IP as the one that you get when trying to telnet to that host?
I once went around and around on an issue similar to this. What had happened was that someone put an entry in the HOSTS file that pointed to a bogus IP.

Good Luck!

Damon

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