Smtp service in IIS is not sending emails

Posted on 2003-11-14
Last Modified: 2010-04-14
Our webserver will not send out emails.    It gives the following message:

"Message delivery to the remote domain "" failed for the following reason:  an internal DNS error caused a failure to find the remote server."

"DNS server unable to interpret format"

This is a web server that sends out password requests, account application responses and order emails.  

The smtp service is running on the machine and the DNS servers are set right in TCP/IP properties.  


Thank you,

Question by:cleighchandler
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LVL 11

Expert Comment

ID: 9750107
r u using a firewall? if yes, make sure that port 25 is open.

Author Comment

ID: 9750150
I never saw a comment to this questions
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Author Comment

ID: 9750156
Sorry, I'm new to this site.  Just getting used to using it...

Author Comment

ID: 9750582
Should there be two domains in the smtp service?
LVL 11

Expert Comment

ID: 9750633
here is a link that will allow you to test your smtp services;en-us;286421&Product=win20

here is a link how to setup those;en-us;303701

to answer your question. I dont think u need two domains for SMTP service

Author Comment

ID: 9751505
Tested the smtp service and this is what it gave me:

"Could not open a connection to host on port 25:  connect failed"
LVL 21

Accepted Solution

marc_nivens earned 500 total points
ID: 9756609
What kind of DNS server is the SMTP server using?  IIS 5.0 sends TCP DNS queries by default, not UDP.  Some DNS servers do not allow TCP queries, firewalls can sometimes only have port 53 UDP open and not TCP, etc... to test this, launch nslookup.  Type "set vc" (no quotes) then run a query.  If it fails, and otherwise works without typing "set vc", then this is your problem.  If this does turn out to be it, get with the DNS/firewall admins and find out where the point of failure is.

Author Comment

ID: 9798805
I'm not quite sure how to figure that out.  I have opened command prompt and started nslookup.  I typed in set vc and pushed enter and it didn't do anything.  Should it bring something back?  

Expert Comment

ID: 9924986
Thanks a million marc_nivens!!  This was the exact problem I was seeing and as soon as I opened up port 53 (TCP) on my firewall the mail started flowing!!  Leave it to good ol' Microsoft to do things differently (like not using the standard UDP port 53 for DNS)...

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