Microsoft Exchange: Unable to deliver the message due to a communications failure
All outgoing e-mail messages (i.e. all e-mails which are leaving the company but not including e-mails to others in the company) are returned with the following error:
Your message did not reach some or all of the intended recipients
The following recipients(s) could not be reached:
eeee on dddd
Unable to deliver the message due to a communications failure
The MTS-ID of the original message is: iiii
ssss Is the subject line of the returned e-mail. dddd Is the date when the message was sent. eeee Is the e-mail address of those the message was to be sent to. iiii Internal exchange ID of the message.
If this is affecting ALL outgoing e-mails then the problem is almost certainly DNS related and indicates a DNS failure.
To confirm this, open a command session on the same server as exchange server is running and enter the following command:
nslookup -type=mx cryer.co.uk
This should run successfully and show mx-dns information for the specified internet domain. An error, similar to:
*** can't find cryer.co.uk: Not implemented
*** can't find cryer.co.uk: Non-existent domain
demonstrates that the error is DNS related.
If the error affects all outgoing e-mails then check the DNS servers. If you can still browse the internet then it is possible that a firewall is blocking MX-DNS requests. Check that your DNS servers are correct and that you can ping them. See also General Network Connectivity Problems.
These notes have been tested with Exchange 5.5 running under Windows NT4.
About the author: Brian Cryer is a dedicated software developer and webmaster. For his day job he develops websites and desktop applications as well as providing IT services. He moonlights as a technical author and consultant.