My users are getting NDRs from our exchange server when they try to send to one external domain only. They can send to all other domains, internal/external, just fine.
Exchange 2003 SP2 running on Windows 2003 SP2. Two exchange servers (one front-end with no mailboxes and one backend, cluster, with all the mailboxes called SERVER). Routing groups set up to send all mails through two smart hosts.
NDR receive by users looks like this:
[Your message did not reach some or all of the intended recipients.
Sent: 1/5/2010 9:34 AM
The following recipient(s) could not be reached:
'mail@ExternalDomain.com' on 1/5/2010 9:34 AM
The e-mail account does not exist at the organization this message was sent to. Check the e-mail address, or contact the recipient directly to find out the correct address.
Enabled diagnostics logging this event appears when NDR is generated:
Event Type: Information
Event Source: MSExchangeTransport
Event Category: Categorizer
Event ID: 6015
Time: 9:34 AM
Categorizer is NDRing a recipient with address SMTP:mail@ExternalDomain.c
om with reason code 0x80070002 (The system cannot find the file specified.
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp
0000: 02 00 00 00 ....
Also mail doesn't appear in SMTP Logs.
Any help would be much appreciated.