We have two domains. One of which is isolated. We're trying to forward mail from one domain, through a DMZ to a relay on the other domain. Using EHLO through telnet works. Using the mail command and specifying the relay works:

mail -S smtp=myrelay.com -s test [email protected]

Sendmail does not work though but claims that the mail would be deliverable:

sendmail -bv [email protected]
[email protected]: mailer relay, host myrelay.com, user [email protected]

sendmail -v [email protected]
mycompany.com: Name server timeout
[email protected]... Transient parse error -- message queued for future delivery

So what's the deal? It says it's deliverable to myrelay.com but then tries to send it to mycompany.com instead. Anyone have any advice where to look to fix this?

1 Answer 1


A "name server timeout" indicates that the name "mycompany.com" can not resolve.

What happens if you do a ping mycompany.com (NOTE: Because of MX records, a failed ping does not mean it's impossible for mail to go there)

While not quite the same as doing a ping text, what does host mycompany.com give you?

Some other useful information can be gleamed from grep hosts /etc/nsswitch.conf

  • mycompany.com is not resolvable as this is a DMZ and only specific hosts can connect to it. The DMZ is suppose to send mail to myrelay.com which then gets forwarded to mycompany.com
    – Jeight
    Feb 5, 2014 at 16:18
  • You can still give it a name by putting it in /etc/hosts for each of the machines that would connect to it. Also, as long as DNSSEC isn't being used, DNS host names can stay private.
    – samiam
    Feb 5, 2014 at 17:25
  • Actually I can't. That's not the purpose of a DMZ. The DMZ is separate from either domain and is used as a middle zone to connect the two domains. I only want it connecting to myrelay.com which will then relay the mail to the correct location.
    – Jeight
    Feb 5, 2014 at 18:05
  • BUT... That got me thinking that I can give mycompany.com the ip of myrelay.com int /etc/hosts. That may be what you meant. That worked. Thank you!!
    – Jeight
    Feb 5, 2014 at 18:30

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