sendmail error 550 - Host Unknown
 

Hi,
I'm new to Linux and need help on sendmail. We have a linux box where I have created some scripts. However, a functionality I need is to be able to send email using another smtp server.
my linux box address is 10.110.10.46 and my smtp server (windows) is 10.110.10.28

This is what I have in my sendmail.cf:
# "smart" relay host (may be null)
DS10.110.10.28

When I type the command
echo this is a test | /usr/sbin/sendmail me@mycompany.com

I get the error:
550 5.1.2 me@mycompany.com... Host Unknown (name server: 10.110.10.28: host not found)

I'm able to ping the server and the smtp server is setup to allow relays from this box

Any ideas?

Thank you for your help

You should put the IP address in square bracketsto avoid nslookups. If that doesn't work you should add an entry in /etc/hosts (or in your dns server, if you use one) for 10.110.10.28, so sendmail can resolve it.

sendmail error 550 - Host Unknown
 

Bathory,
Thanks for the suggestions. I had already put the IP in the /etc/hosts.

I found the solution. This is what happened:

When I read the Redhat documentation, it said that I needed to created the sendmail.cf in the /etc/mail folder. That's what I did. Apparently the changes I made never worked because the system was looking at the /etc/ folder and not /etc/mail folder for the sendmail.cf. So just to give it a try, I re-created the sendmail.cf in the /etc/ folder and it worked. The problem was then with the documentation.

Thanks again.