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Exchange recieving mail but not sending

Posted on 2005-03-29
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Last Modified: 2008-03-03
Hi

We have a mail server running Windows 2000 Server and Exchange 2000. We are experiencing a problem with mail not sending out. We are able to recieve mail from external sources 100% but all sent items are not going through and the mail queue is constantly growing. If I look open Exchange System Manger
Under 'First Organization' (exchange)
 -->expand 'Servers'
  -->expand 'MSTMAIL' (our mail servers name)
  -->expand 'Protocols'
   -->expand 'SMTP'
    -->expand 'Default SMTP Virtual Server'
     -->expand 'Queues'
I am able to see all the sent emails retry or present in the mail queue.

By right clicking and selecting properties of one of the mail an error stating 'Unable to bind to destination server in DNS' is displayed in the error box.

Please could you help in trying to sort this problem out and advise to possible solutions.

Many Thanks
Mustekkzn
 
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Question by:mustekkzn
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11 Comments
 
LVL 104

Expert Comment

by:Sembee
ID: 13651796
Verify that you can connect to your ISPs SMTP server:

telnet smtp.isp.net 25

(replacing smtp.isp.net with the actual address of the ISPs server).

Then try to an external server:

telnet maila.microsoft.com 25

Depending on whether all or none of those work will indicate where the problem is.
If you cannot connect to anything then the problem is somewhere locally.
If you can cannot to your ISP but not to Microsoft then the issue is with your ISP. If that is the case then setup an SMTP Connector to send the queue content out via your ISP (http://www.amset.info/exchange/smtp-connector.asp). Then call your ISP to ask what is going on.

If you cannot to Microsoft then it isn't traffic that is being blocked, the DNS error you are getting might be correct or maybe a red herring. How have you got your DNS configured at the moment?

Simon.
0
 

Author Comment

by:mustekkzn
ID: 13651909
Hi Simon

We are successful in telneting to our ISP and microsoft from our ISA server but if we try both destinations (our ISP and microsoft) from our actual mail server an error pops up stating 'connection lost'.

We already tried setting up an SMTP Connector to send the queue content out via our ISP but all that happened is that all the mail that was in the orginal queue moved to the new SMTP Connector and after that just sat there and didnt send out.

We do have DNS configured at the moment.

Thanks
Mustek
0
 

Author Comment

by:mustekkzn
ID: 13651939
Apologies. My comment regarding DNS above doesnt make sense and I will provide a breakdown as to how it is configured at the moment.
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Author Comment

by:mustekkzn
ID: 13652086
Hi Simon

With regards to explaining how we have DNS configured at the moment, could you maybe ask a few questions that we could answer straight, that would help us explain and you understand how we have our DNS configured?
On our Domain we have 3 Domain Controllers one of which is our DNS Server, an ISA and Proxy server.
Up until today the mail has been going out 100% and our mail server has not given us any hassles.


Cheers
Mustek
0
 
LVL 104

Expert Comment

by:Sembee
ID: 13652689
Your DNS should be configured with all the servers and workstations pointing to the domain controllers for DNS ONLY, and the Domain Controllers pointing to themselves for DNS. No external DNS servers should be in the configuration.

Is your Exchange server behind the ISA server? If so that looks like it is the cause of the problems - especially as the tests work from the ISA server itself.
However do one last check.

On the ISA server use NSLOOKUP to find the IP address of maila.microsoft.com
Then go to the Exchange server and try the telnet test using the IP address:

telnet 123.123.123.123 25

Where 123.123.123.123 is the IP address that your server looked up.
If it works with the IP address then it is DNS.
If it still doesn't work then the traffic is being blocked, probably by your ISA server.

Simon.
0
 

Author Comment

by:mustekkzn
ID: 13653406
Hi Simon

These are the steps I took from the ISA server. Opened 'command prompt'.
 cd\ to get to the root directory. Then I typed in 'NSLOOKUP maila.microsoft.com' this is what it returns.

   Server: mstintranet
   Address: 192.168.111.5

***mstintranet.dbn can't find maila.microsoft.com: Non-existent domain

Am I using the NSLOOKUP tool incorrectly?

With regards to the rest of your comment above. Yes, the Exchange server is behind the ISA Server and I am also starting to believe the problem is at the ISA side on not necessarily on the exchange server.
With regards to the DNS configuration. We have 3 DC's and one of them is also a DNS server. The DC's are setup to point towards the DNS server and no external DNS servers are configured.

Hope this helps us get closer to a solution. Thanks for your assistance thus far.
Mustek
0
 
LVL 104

Expert Comment

by:Sembee
ID: 13654924
First thing I would suggest, especially if you have three domain controllers is to make at least one of them a DNS server. It is always a good idea to have more than one. You may also want to check whether you have more than one global catalog. If you don't, then one of the others can take that role.

You are doing NSLOOKUP correctly, so it looks like it is DNS that has the problem.
For reference the IP addresses that I get are 131.107.3.125 and 131.107.3.126.

Was that test on the ISA server?
If so, find out what your ISPs DNS servers are.
Check that you can ping them. Then repeat the NSLOOKUP, but do it like this:

NSLOOKUP (enter)
SERVER 123.123.123.123 (enter)
(where 123.123.123.123 is your ISPs DNS server).

then type maila.microsoft.com and see what you get back.

If that works, then your ISP is blocking DNS requests to the root servers. If that is the case then you will need to configure forwarders.

Start the DNS applet and connect to your DNS server. Right click on the server and choose Properties. Click on the tab "Forwarders" and enter your ISPs DNS servers.

Simon.
0
 

Author Comment

by:mustekkzn
ID: 13659563
Hi Simon

Firstly. the test was conducted on the ISA server.

From the ISA server I am able to ping our ISPs DNS server, however conducting a NSLOOKUP from the ISA to our ISPs DNS does not work.

Mail in the queues are constantly filling up with mail to 'Postmaster' which have popped up every now in the past but never this much, this frequecntly.

Do you think I should still configure another DC to become to a DNS server.

Mustek
0
 
LVL 104

Accepted Solution

by:
Sembee earned 2000 total points
ID: 13660998
My advice on configuring another DC to be a DNS server will have no impact on this particular problem - it is just something that you should do. Having a single DNS server puts your network at risk if that one server goes down.

postmaster@ messages are emails bouncing. They are probably internal messages that cannot get out, or failed message that came in but cannot get back out again.

Can you do the telnet test to your ISPs SMTP server from the Exchange server - even by IP address? If you can, use an SMTP connector to get the email out, setting it to use an IP address and not the DNS name of your ISPs SMTP server. This isn't a good long term resolution, but it should get your email flowing again.

Otherwise it is your ISA server that is at fault. ISA is not an area I have experience in - I have never deployed it for one of my clients so wouldn't even know where to start looking for problems with it.

Simon.
0
 

Author Comment

by:mustekkzn
ID: 13661300
Hi Simon

We managed to fix the problem and this is how we came about fixing it.
On the DNS server we took our ISP alternate DNS address and added this address in
Open Exchange System Manger
Under 'First Organization' (exchange)
 -->expand 'Servers'
  -->expand 'MSTMAIL' (our mail servers’ name)
  -->expand 'Protocols'
   -->expand 'SMTP'
    -->right clicked 'Default SMTP Virtual Server' and select properties
Select the 'Delivery' Tab
 Click 'Advanced'
  Click Configure

and here we added our ISPs alternate DNS which we got from our ISA server.
After doing this, hey presto, mail started flowing once again.

I will be awarding all the points to you, but I would like to let you know exactly why I am doing so.
Firstly for your quick and timely response. I have had, and still have, posted questions that sit a while and take a while to have comments posted, but your response and comments came very timeously.
Secondly for your advice on making another DC a DNS server which will in turn lower the risk and problems associated with only having 1 DNS server. I will be implementing this feature.
And thirdly, for providing me with a better understanding of NSLOOKUP, telnet, postmaster messages and setting up a SMTP Connector (which will CETAINLY relieve pressure if this problem had to occur in the future) which I now know how to setup and implement 100%.

Thank you for your assistance. It has being a pleasure working with you.
Many Thanks
Mustek



     
0
 
LVL 104

Expert Comment

by:Sembee
ID: 13661427
Excellent. Glad to hear that you have got it fixed.
Thanks for the points.

Simon.
0

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