Exchange 2K not delivering

Mail may form a queue to remote Exchange computers until an expiration time-out occurs. A non-delivery report may be generated that is similar to:

test@microsoft.com on 6/11/2001 12:39 PM
Could not deliver the message in the time limit specified.
Please retry or contact your administrator.

< alias ex2000.dotnet.net #4.4.7>
This problem does not occur with computers that are not Exchange 2000 servers. This problem also does not occur with Exchange 2000 servers that return a fully qualified domain name (FQDN) in the initial response.

Exchange 2000 uses an ESMTP extension that is not standard for authentication. In accordance with the relevant Request for Comments (RFC) document, this non-standard extension is prefaced with X-.

This extension (X-EXPS) is implemented as a protocol sink in the Microsoft Windows 2000 Simple Mail Transfer Protocol (SMTP) service. This protocol sink uses the initial response from the server to determine whether a computer is local to theExchange organization or is outside the Exchange organization.

The name that the server reports (whether it is a FQDN or not) is passed to Windows 2000 application programming interface functions to determine the location of the message. An error is returned from this function for names that are not FQDNs.

Exchange 2000 notes the error and determines that it can try to deliver the message again. Therefore, the message stays in the queue, and Exchange 2000 continuously tries to deliver the message until the time-out occurs. The message eventually generates a non-delivery report that is similar to the NDR in the "Symptoms" section of this article.

To resolve this problem, obtain the latest service pack for Microsoft Exchange 2000Server. For additional information, please see the following article in the Microsoft Knowledge Base:

Q301378 XGEN: How to Obtain the Latest Exchange 2000 Server Service Pack

1) did you verify the file version from the MS article?
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q301401

File name Version
Exps.dll 6.0.5683.00

2) underscore is NOT part of a *VALID* FQDN. How the server chooses to handle this is anyone's guess.
""

and from that article above:
Inside the Exchange organization, virtual servers with an FQDN that is not valid or a name that is not an FQDN may not be able to receive mail correctly. This is the case both before and after you apply this fix.

So.. drop that _ asap! If you want to distinguish it, use a - instead.

Also note, that Exchange to Exchange mail is *NOT* handled 100% to RFC spec's for SMTP! So again.. anything odd could happen.

3) did anything show up in the error log of the exchange server?

4) have you tried to manually create SMTP mail FROM the server by telnetting to the destination?

example:
telnet some.host.mail.server 25

this opensa telnet window but to port 25 (smtp) on "some.host.mail.server"

do this FROM the mail server, and the "some.host..." should be the SMTP server that the mail that's failing is going to.

If you can manually enter mail by telneting to the destination FROM your mail server, then you know the problem *IS* your mail server.. and you may need serious exchange help.

5) related to 4 .. have you checked that you're not on an ORBS list or some such and that mail from your server is being denied/rejected?