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Need to Flush DNS each time try to send email to yahoo.com domain from ms outlook through an Exchange 2007

We have an Exchange 2007 on windows server 2003 ,
There is a problem when sending emails to yahoo.com domain,
If a user try to send email from MS Outlook client it will stuck in the exchange's queue (with error: Last Error: 421 4.4.2 Connection dropped),
But if the same user uses OWA and send an email to the same yahoo account it will go thorough and also will clear the yahoo.com queue and previous emails which were send from outlook will receive their destination at yahoo too.
If the users do a " ipconfig /flushdns" command on their computers before sending the email through outlook client , they will be able to send the email to yahoo.com but after some hours it will stop again,
While there is no problem through OWA>
The users are receiving their IP and DNS information from DHCP on AD, and the DNS is pointing to the same AD server.
Please help.
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guruconsult
Asked:
guruconsult
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2 Solutions
 
steinmtoCommented:
The server does the dns lookups for the email not the outlook client so I am not sure why ipconfig /flushdns on the client would do anything.  Have you checked the servers dns?  Are you using fowarders?  
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guruconsultAuthor Commented:
You right , may be it was a coincident , because when I do the flush the dns on client today it is not working,
 
I checked the server's DNS we do have forwarders to 8.8.8.8 and 8.8.4.4 , I tested by removing them too.
the server is able to resolve the yahoo.com mx record when I set type=mx in nslookup.
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steinmtoCommented:
Are you on a greylist or blacklist?  Check www.mxtoolbox.com to see if you are on a blacklist.  Have you tried to telnet to the yahoo email servers to see if they return a message?  
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guruconsultAuthor Commented:
I am not a blacklist, tested domain and PTR in mxtoolbox.com.
The PTR is pointing to the correct record.
I just sent 5 emails from outlook, all five stuck in the queue, this time flushing the dns on server or client didn't help.
But as soon as restarted DNS service on server , all 5 left the queue and hit the yahoo.!!
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steinmtoCommented:
Is your dns server up on the latest Service Packs and Patches?  It sounds like a dns issue with Yahoo.  I would also try the telnet test just to make sure there is not a problem with the email to yahoo.

See telnet test.

http://support.microsoft.com/kb/153119
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guruconsultAuthor Commented:
I was able to telnet to port 25 of all 13 yahoo's mx servers with no problem and seeing the header,
it accepts the HELO command, but when try to send test email it gives error on the MAIL FROM command:
MAIL FROM: administrator@mydomain.com
501 Syntax error in parameters or arguments

Also windows updates does not have any updates for me, is there any other place to check for DNS updates?
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steinmtoCommented:
You are running Service Pack 2 correct?
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guruconsultAuthor Commented:
Yes,2003 Enterprise SP2 64bit
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steinmtoCommented:
Can you take out the fowarders restart dns and then try it.
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steinmtoCommented:
Or try
64.22.192.4
64.22.192.3
as your fowarders as a test.  They are a local isps public dns servers.
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guruconsultAuthor Commented:
I should wait some time so it stop working again, right now it is working and it is usually good for about 5-6 hours, I will check these after that.
Thanks
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guruconsultAuthor Commented:
Ok, I changed the DNS forwarders, removed them, didn't change anything,
Actually I have more details now:
1- Nothing on the client side will force the queue to empty itself and send emails to yahoo.
2- If I restart the DNS service and send one email to yahoo , it will g through as well as all other emails to yahoo which were stuck in the queue !!!
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ChiefITCommented:
DCdiag /test:DNS

Enable recursion and put back your forwarding servers of 8.8.8.8 and 8.8.4.4
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guruconsultAuthor Commented:
One of the root servers's IP was wrong, changed it , but still not working,

I have outlook on of the domain controller servers, and able to send emails to yahoo.com from there with no problem.
As soon as any user from their workstation's outlook send an email to yahoo.com , that email stucks in the queue and as well as any other emails I send from my outlook on the server,
I should restart the DNS service, clear its cache, flush dns by ipconfig /dnsflush , and then send another email from my server's outlook, that email will be received in yahoo and also will release all emails stuck in the queue !!
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ChiefITCommented:
If your folks are able to contact yahoo.com while the email queues are stuck, this means it's a problem with the mail server's preferred or alternate DNS server listed on the nic configuration. OR, your mail server has a bad HOST A record  within the HOST file:

So, how do the clients interact with yahoo when the mail queues are stuck?
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guruconsultAuthor Commented:
We (server and clients) are able to contact yahoo.com domain while the emails stuck in the queue.
there s no A record in the host file related to yahoo.com.
Both preferred and alternate DNS servers listed on the nic are able to resolve yahoo.com mx records and both return the same results.
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ChiefITCommented:
Then it appears your Mail server may have DNS poisoning from a bad HOST file on that computer. You see, when a computer resolves DNS it will look within its DNS cache first, then in the Host file. That is found in C:\Windows\system32\drivers\ect\Host. Since it's your mail server that appears stuck. I would check that file on the mail server.

DNS poisoning is usually the result of a malicious attack. So, I would certainly look for malware on any computer that has a poisoned host file.

The route of a DNS query:
 http://www.experts-exchange.com/Networking/Protocols/DNS/A_323-DNS-Troubleshooting-made-easy.html
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guruconsultAuthor Commented:
Thanks, I have checked the server's host file before, I will check the client computer's host file as well and see if we can find anything.
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guruconsultAuthor Commented:
The client and servers were able to resolve yahoo.com and its mx records with no problems.
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ChiefITCommented:
How's it going with this issue?
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guruconsultAuthor Commented:
Still the same, did not find any problem with host file, dns servers, everything looks fine, and able to send emails to every where, except yahoo.com and that just when try to send it from outlook, owa works fine.
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guruconsultAuthor Commented:
No solutions :-(
Closing the request
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guruconsultAuthor Commented:
Not a solution, just closing the request
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