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Unable to send email to one domain

Posted on 2011-03-21
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Last Modified: 2012-05-11
For a couple months now we have been unable to send email to one particular domain.  This is a client of ours and it makes it difficult to communicate between two project managers.  I hoped it was a glitch and let it go for a while.  A couple weeks later we had our Exchange 2003 server assessed for health and a few things were "repaired" that solved an unrelated problem but it did not solve the sending issue.  

That is when I solicited help from the IT department of our client.  As I expected, they said it must be on our end because they have no trouble receiving email from anyone else.  And we have no problem sending to anyone else.  Plus they were moving to a new location and that delayed things a couple more weeks.  

I then solicited help from our service provider who couldn't discern the problem but suggested that our client add our domain name to the "allowed senders list" in mxlogic that they use for spam control.  Our client added our name to the allow senders list and messages that were sitting in our queue for their domain were immediately delivered to them.  Great! I thought.  I sent a response to them and it sat in the queue for at least a day and then was delivered sometime over the weekend.  Now i have sent another email to them and once again the email is sitting in our SMTP queue in delayed status.  The queue information says "The remote server did not respond to a connection attempt".  It seems like their server is not accepting requests for mail delivery from our server.

If I send a tracert to their email server I see multiple time outs before it then goes on to complete the trace.  Could that be happening to the emails?  Could it be that their server can't talk back to ours to validate?  Isn't that the normal process for email delivery?

Any ideas?

thanks,
kevin
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Question by:12vltmn
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by:Alan Hardisty
ID: 35182925
Please have a read of my article which gets you to check your configuration and basically make sure you are RFC compliant:

http://www.experts-exchange.com/Software/Server_Software/Email_Servers/A_2427-Problems-sending-mail-to-one-or-more-external-domains.html

If you have any questions, please let me know.

Alan
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by:dtrance
ID: 35182930
The trace route isn't a good test.
Instead try telneting to the destination mail server instead.

telnet <IP of mail server> 25

If you get a response than SMTP traffic is possible.  If not, than you have found your problem.
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Expert Comment

by:stowyo
ID: 35182959
I would guess that you are on a RBL (Realtime Black List) for one or several reasons.  

(1) Check to see if you are an open relay
(2) run the tests on the internet to see if you fail any tests...
(3) PTR record should exist in your DNS for your mail server too

You may have to create a separate connector for this domain if all else fails

- Stowy
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Author Comment

by:12vltmn
ID: 35183215
dtrance:  I did try the telnet and was successful with a 220 response.

stowy: I checked the two sites that alan lists in his article and both were clean.

alan:  I am reading your article.
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by:dtrance
ID: 35183271
If your getting a 220 response then your mail system is able to talk smtp to the destination host.  We are also assuming there is no relaying involved and mail is sent directly.

If thats the case, then perhaps there is a DNS problem.  See if you are getting the correct destination mail system for the domain in question

nslookup
> set type=mx
> example.com
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by:fireline1082
ID: 35183273

I believe if you are able to send mails to other domains or partners and also receive mails from them; then there should be no issues from your End

It is the other company that needs to double check; ask them to send you an email and see if there is any NDR (non delivery report) generated - if so ask them to pass it to you via hotmail or gmail

This should give you the the root cause


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by:stowyo
ID: 35183279
Here is an article on EE about what I have had to do for Exchange to send to AOL in the past.  It could be similar for this domain that will not accept your email.  http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_23243965.html.

Basically you create a second queue for email that goes to this domain.
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Author Comment

by:12vltmn
ID: 35190905
ALAN: I read your article and followed your procedures.  

Reverse DNS from email server IP address to our mail server domain successful.  From the mail server domain name to the IP address successful.  When I reverse DNS just our domain name it returns the IP of our on-site web server.

Our email server IP address had no blacklist hits.

Our Internet reputation is Neutral (we had a problem about 6 months or so ago with our web server being attacked and we had to reinstall our web server [and did so on an entirely different machine])

The SPF record search returned null so I generated one on the other site and send it to our provider who has not added that to our zone (as of last night at 6 pm mountain time).

It appears the SPF record was the only thing that needed attention.  But I still have two emails sitting in delayed status in our SMTP queue.  It is still not flowing to this one recipient.  The queue information states "the remote server did not respond to a connection attempt".  They have been sitting there for over 24 hours now.

FIRELINE: They can send us email with no apparent issues.  We received their email but cannot respond.
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Author Comment

by:12vltmn
ID: 35190926
CORRECTION:  our provider HAS entered the SPF record as of last night at 6 pm
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by:dtrance
ID: 35190981
Again, is the DNS server your mail system is using, sending to the correct mail server for the domain in question?

Do the mx lookup
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Author Comment

by:12vltmn
ID: 35191304
DTRANCE:  sorry, yes it is resolving to the correct mail server with mxlogic information.  They are using MXLOGIC.net.
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Expert Comment

by:Alan Hardisty
ID: 35192793
If you like - drop me a test email to alan @ it-eye.co.uk and I will see if I can detect a problem with your configuration using my Anti-Spam logs which will tell me everything I need to know.

Alan
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Author Comment

by:12vltmn
ID: 35193746
ALAN:  I will send an email.
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by:Alan Hardisty
ID: 35194002
Thanks - let me know when it has gone and I'll look out for it.

Alan
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by:Alan Hardisty
ID: 35194026
Got it - checking now.
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Accepted Solution

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Alan Hardisty earned 500 total points
ID: 35194049
Well - you look RFC Compliant to me.

You mentioned the following in your email:

"I may have found the problem to our email issues with the single domain.  On our email server, in the TCP/IP config, the manually configured DNS servers were set to our internal DNS server first, and an external DNS server as the secondary.  I swapped the order to make our internal the secondary and it now appears that email to that domain is flowing.  The SPF record may have helped also and perhaps the combination of the two did the trick."

Your server should only be configured to point to your internal DNS server to resolve DNS queries, not an external server.

On the DNS server, under the forwarders tab, you may need to add the DNS Servers of your ISP to the Forwarders tab so that any unresolved DNS queries that your server cannot answer will get forwarded to your ISP's DNS servers.

Have you got forwarders configured on the DNS server properties?

Alan
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Author Comment

by:12vltmn
ID: 35194463
ALAN:  I did not have the forwarders configured.  I had to reinstall that server a while back and must have overlooked that.  I had my ISP as a DNS server in the NIC's TCP/IP properties instead.  I changed the config to only list our internal DNS servers as primary and secondary and added the ISP's three DNS servers as forwarders on the primary DNS server.  And I changed the mail server's NIC TCP/IP properties to now only point to our internal DNS servers.  I will test.
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by:Alan Hardisty
ID: 35194482
It's easily overlooked especially if you have to rebuild!

Fingers crossed it's all it takes.
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Author Comment

by:12vltmn
ID: 35194692
Email to that domain is flowing.  Sweet.  Thanks!
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