Sendmail smarthost

[rsp11]

Question: On Solaris box.
Does anyone know if there is an entry for a smarthost in the sendmail.cf file and the dns server this box uses dies does the server still send it's messages on.

What happened was our dns server died.
The mail relay is configured as a split dns so it's dns was fine
A server had an entry for the smarthost as mailrelay.domain.com which was recorded in the servers host file.
But mail stopped leaving this server for the mailrelay

So does Sendmail ignore dns when there is and entire for the Smarthost?

 

[mrballcb]

You're saying that the sendmail server has a dns server on it, but your company's dns which serves all other machines failed? Does the smarthost use that company dns? If so, it probably started rejecting mail from your sendmail machine because the sending machine hostname no longer resolved.

Take a look in your sendmail maillogs and see if the problem is that the sendmail couldn't resolve (sounds unlikely the way you've described it) or that the remote system was rejecting the email with some tempfail (400's) or permfail (500's) message.

 

[rsp11]

It's political, I don't have access to the server with the problem but I manage the DNS servers and the mail relay.

The server with the problem is configured to send all mail to my mail relay but one of the DNS servers died. Now although the seconday DNS was alive I can't confirm that the problem server had this configured in it's resolve.conf file.

The problem server only sends mail for it's self to the mail relay (mailhost.domain.com) which was configured in the sendmail.cf file under Smarthost and was in the /etc/host file with the releven IP. So my question is, and I know it's difficult for you guys to see the full picture but shouldn't this have still workded doesn't the Smarthost entry tell Sendmail to ignore lookups and just send the mail to the relay??

 

[mrballcb]

Sendmail always does a dns lookup. If you put a hostname for the smarthost, it tries to ask the dns server. Theoretically, if you put [xxx.xxx.xxx.xxx] as the smarthost, it won't do a lookup (the [] notation prevents a lookup). But I've not tried this, so I don't know if the smarthost function accepts the [] notation like it does in email addresses. Try it and see what happens is the best I can suggest. It's easy enough to revert back to the previous sendmail.cf if it doesn't work as expected.

 

[rsp11]

thanks mrballcb