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SOA Serial numbers do not match

I'm having problems sending emails to certain email domain. I am running EX2003 server. I ran the SMTPDiag tool and it came up with "SOA serial numbers no match" error. Does anyone know what the error means? Any help is greatly appreciated.

Searching for Exchange external DNS settings.
Computer name is TAUSINIO.
VSI 1 has the following external DNS servers:,
VSI 3 has the following external DNS servers:,

Checking SOA for bluesky.as.
Checking external DNS servers.
Checking internal DNS servers.
Serial numbers do not match: 42676  2007020202
Serial numbers do not match: 42676  2007020202
Serial numbers do not match: 42676  2007020202
SOA serial number match: Failed with one or more failures.

Checking local domain records.
Checking MX records using TCP: ascc.as.
Checking MX records using UDP: ascc.as.
Both TCP and UDP queries succeeded. Local DNS test passed.

Checking remote domain records.
Checking MX records using TCP: bluesky.as.
Checking MX records using UDP: bluesky.as.
Both TCP and UDP queries succeeded. Remote DNS test passed.

Checking MX servers listed for ethan.lake@bluesky.as.
Connecting to mx01.blueskynet.as [] on port 25.
Successfully connected to mx01.blueskynet.as.
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1 Solution
SOA errors are DNS errors. They have nothing to do with Exchange.
If you have multiple internal DNS servers then one of them is probably not replicating with the others in a timely manner.

iemmsleyAuthor Commented:

I only have one internal DNS server. How do I fix this problem?
If you only have one internal DNS server then you shouldn't have this problem.

Do you have external DNS servers in your network configuration? If so, remove them. Rule number one with AD domains - no external DNS servers in the network configuration of any AD clients - servers, workstations or domain controllers.
If you need to use external DNS servers then configure forwarders in the DNS Server applet on the domain controller.

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iemmsleyAuthor Commented:
All my network configs are pointing to my internal DNS. My Internal DNS already has DNS forwarders configured to an my ISP DNS servers.

Its weird because I ran SMTPDiag to other domain name and they go through without a problem.

Do you think this is causing you a problem?
If you don't see any problems with DNS then I would tend to ignore the message.

It isn't clear from your original question whether the domain you were testing was an internal or external domain. If it was an external domain then the problem is out of your control anyway.

The person submitting was probably trying to troubleshoot why the Outlook clients run slow sometimes....and going thru the Exchange Troubleshooting document provided by Microsoft.

DNS and Exchange are related, because Exchange uses DNS to deliver mail, even internally. That's what the smtpdiag.exe tool is for.

Let's say that DC1 is the "first" domain controller, and DC2 is the "second". Both are internal, on site.
When you run the smptdiag.exe tool, it checks SOA for the domain.
Then, it checks tcp/udp SOA serial # using the 'first' dns server.
It will tell you if it fails or not.
Then, it checks the 'second' DC.
The error coming back is:
Failed: DNS server (IPAddy) may be down
DNS server (IPAddy) did not return a valid SOA record.
SOA serial number match: Failed with one or more failures.

I think the question is "how do you fix that".
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