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Exchange 2000 Not Trying Next MX Record

By Viperian ·
Hiya,

I have a big problem with a Exchange configuration. Server is a Windows 2000 server with SP4 and Exchange 2000 server with SP3 + SP3 Post september 2003. After applying these Service packs the trouble started. DNS correctly gets all mx records for email directed to the outside world.

Problem:

For a customer where i have to deliver email there are 3 mx records available, namely (fiction)

mail.customer.nl 10 mx preference (unreachable)
fallback.customer.nl 20 mx preference (unreachable)
relay1.isp.nl 100 mx preference
(active)

Exchange tries to deliver to the first 2 adresses and then stops. It doesnt deliver to the relay server.

I have the same problem with other adresses where the first is their own mailserver and second or third is a relay server with an provider.

If the first or second mx record is up there are no problems with mail delivery.


The problem is if their are more then 1 MX record and the 1 or second mx record

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by Viperian In reply to Exchange 2000 Not Trying ...

Seems like the last line died on submit.

I was trying to tell that if the servers pointed @ by the first or second MX record are unavailable the server doesnt deliver the email even if there is a third or fourth MX record pointing to a relay server which is Active and accepting email.

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by CG IT In reply to Exchange 2000 Not Trying ...

your problem may not be with you but with the relay servers at the ISP. An active relaying mail server is virtually unheard of nowadays with the focus on spam prevention so before pulling your hair out and popping the vallum that the problem is yours, check with the ISP guys and see if they've done something on their end like no longer allowing relaying.

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by Viperian In reply to

I dont use a relay server i deliver the mail through DNS direct to the addressed party. I can also see that outgoing mail is only directed to the first mx record and sometimes the second mx record. These problems arose after installing SP4 for Win2K and SP3 for exchange 2000, before that the problems werent there.

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by mjost In reply to Exchange 2000 Not Trying ...

When this happens are there any Event log errors -ie Non-Delivery Reports Event ID 756 or Event ID 4000 messages logged in the Application Event log? Or is this mail sitting in the queue awaiting delivery?
Are you using a SMTP front-end servers?
ISP using dial-up connections?

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by Viperian In reply to

There arent any NDR reports or other event log messages, also i dont use a front-end server construction. Also not using dialup usingT1 as a connection straight to internet.
Exchange tries to deliver the message to the external recipient, but stops with the first or second mx record. If those two give errors like 10051 (netowrk unreachable) and timeout it waits for the next time it is triggered for delivery.

Momentairly i use a smtp gateway infront of the exchange servers (smart host), which solves the problem but if i switch back to letting exchange deliver the emails straight forward through dns to the internet it fails with some.
so solution must be found in exchange 2000, but still haven t found it yet

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by mjost In reply to Exchange 2000 Not Trying ...

ok, Turn on full debug reporting and test it again to see whats up with the outbound email.

Enabling Debugging Level Logging If you are experiencing mail flow issues and want to view all events, you can modify a registry key to set logging to the highest level (level 7).

To setup troubleshooting Mail Flow

To enable logging at the debugging level
1. Start Registry Editor: From the Start menu, click Run, and then type regedt32.
2. In Registry Editor, locate and click the following registry key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\ MSExchangeTransport\Diagnostics\SMTP Protocol
3. Set the value to 7.

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by mjost In reply to

Also, assuming your DNS is correct, the outbound messages are routed to the connector or to the outbound SMTP virtual server that is responsible for delivery. Check for very simular Virtual Server names which cause issues I understand.

Is this on a DC? If so, instead of modifying the default SMTP virtual server, it is recommended that you either create an additional SMTP virtual server or create an SMTP connector to override the default virtual server settings. In many instances, it is preferable (but not required) to set up an SMTP connector to handle outbound mail.

To configure your SMTP virtual server to deliver outbound mail you must:
Ensure that the outbound port is set to port 25 (this is the default setting). Allow anonymous access for your outbound connection (this is the default setting). Set external DNS servers for SMTP to use, if desired. You can configure the SMTP virtual server to use an external DNS server; however, it is easier and more common to rely on your internal DNS servers to forward mail to trusted external DNS servers.

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by Viperian In reply to

Poster rated this answer.

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by Slartibartfast In reply to Exchange 2000 Not Trying ...

OK, The first thing you have to do is check whether your DNS server is able to resolve the smtp server referenced by the failing MX record (using nslookup from a DOS prompt on the *Exhange Server*.

If it can , then (also from the dos prompt) see if you can actually establis a session on Port 25 with the recipient server. A little-known but incredibly useful way of testing this is to use Telnet from the DOS prompt, so in your case 'Telnet relay1.isp.nl 25' (the 25 tells it to use the SMTP port). If the server is reachable, you'll see the DOS screen clear and the SMTP welcome prompt.

My guess is that you won't be able to reach the server this way. If you can't, then try it from another computer not on your network. If that can't either, it's probably the recipient server, not Exchange or DNS

Andrew.

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by Viperian In reply to

DNS is able to resolve the addresses tested with nslookup, also can telnet to port 25 from command prompt. This problem arose when W2K got up to SP4 and exchange 2000 got up to SP3. Also loaded all hotfixes suggested by Microsoft. I now use a workaround with a email virus scanning gateway which works fine.

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