Unable to bind to the destination server in DNS (Full Version)

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vmitmgr -> Unable to bind to the destination server in DNS (12.Oct.2006 3:49:59 PM)

Hi.  I'm having problems sending SOME message.  They sit in queue with the queue information: Unable to bind to the destination server in DNS.

From my Exchange 2003 server, I can ping these domains.  nslookup resolves the mx record and I can ping those servers.  (Some at least.  I'm assuming some just don't respond to ping.)

But the messages don't go.  I've rebooted my DNS servers and exchange.  Didn't make any difference.  I can't find anything else that might cause this except one site that said recent changes to IIS might be an issue - there haven't been any changes on this server in months.

Receiving seems fine.  Sending to the majority of sites seems fine.  I can't find any indication that we are black listed.

Any help is greatly appreciated.  Thanks in advance.



uemurad -> RE: Unable to bind to the destination server in DNS (12.Oct.2006 4:00:01 PM)

Try a manual telnet test on port 25 from your Exchange server to the IP address of one of the destinations you can't send to.  Let me know if you need assistance on the SMTP commands within the telnet session.



vmitmgr -> RE: Unable to bind to the destination server in DNS (12.Oct.2006 4:06:14 PM)

Thanks for the response.

I was able to telnet to port 25 on one of the remote servers.  I don't know any of the smtp commands to test beyond that.




uemurad -> RE: Unable to bind to the destination server in DNS (12.Oct.2006 4:43:31 PM)

  None of the commands below are case-sensitive
The braces {} denote comments - don't include in the commands

TELNET outsideIPaddress 25  {the 25 indicates TCP port 25}
HELO testmessage.com  {EHLO can also be used}
MAIL FROM:testuser@yourdomain.com
RCPT TO:actual.user@outsidedomain.com  {this needs to be an actual address within their Exchange environment}
DATA
SUBJECT:Test message from the you at yourdomain.com
This is a test  {this starts the body of the message}
Please don't respond
           {Note there is a blank line - press Enter without anything else}
.           {A single period followed by Enter terminates the message body}
QUIT        {Terminates the Telnet session}



de.blackman -> RE: Unable to bind to the destination server in DNS (12.Oct.2006 9:40:30 PM)

Have you by any change configured "external DNS servers"  on the properties of the SMTP virtual server in the exchange system manager?  If so, remove them.



vmitmgr -> RE: Unable to bind to the destination server in DNS (13.Oct.2006 8:59:16 AM)

We have not changed anything in our configuration for at least 2 weeks.  The first message we can identify as being "hung up" in this way was sent on 10/11 in the early afternoon.

Here are the results of a manual message conversation.  This was done from the email server.
====================================================
telnet external.com 25
220 Antispam.external.com ESMTP Symantec Mail Security
HELO mydomain.com
250 Antispam.external.com
MAIL FROM: me@mydomain.com
250 OK
RCPT TO: recipient@external.com
250 OK
DATA
354 End data with <CR><LF>.<CR><LF>
SUBJECT: suject text
Message line 1
Message line 2

.
250 OK: queued as 4C47955EA81
QUIT
Connection to host lost
=====================================================

It certainly appears to me that I was able to manually send a message.  I guess we'll see if I get a response.  We still have 3 messages in queue to this domain which will not go.  And there are 3 other domains with similar errors.  (I haven't tested a manual message but I did check resolution of the MX record to each and it works.)

I'm totally stymied.

Really appreciate your help.



vmitmgr -> RE: Unable to bind to the destination server in DNS (13.Oct.2006 9:31:14 AM)

FYI - the test message sent manually was received.  The recipient replied.

(Can I go home now?)



vmitmgr -> RE: Unable to bind to the destination server in DNS (13.Oct.2006 10:58:09 AM)

I'm still plugging away at this.  I have discovered that apparently there is no reverse lookup for my mail servers IP address.  Seem to be some indication this could cause problems on a site by site basis rather than global.

Guess I'll have to learn tinydns today :-(



uemurad -> RE: Unable to bind to the destination server in DNS (13.Oct.2006 11:09:28 AM)

Without reverse lookup, some systems will reject your message, but you'll get an NDR to the effect of "you don't have permissions".  The results to those domains will be consistent, not intermittent.

Some mail carriers use it to cut down spam.  Many spammers try to spoof, or use open relays, or use zombie systems to send out their garbage.  AOL and Hotmail are the carriers I see most often mentioned.



de.blackman -> RE: Unable to bind to the destination server in DNS (15.Oct.2006 1:58:09 AM)

download and install Exchange troubleshooting assistant from microsoft's website. It has a neat section for troubleshooting mail flow issues.



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