I'm trying to configure sendmail on our Debian Linux server to send mail, using our Exchange server as a relay. I'm a total noob at all of this.

We can send mails to internal addresses (for example, if our domain name is ourdomain.com, the server can send mail to bob@ourdomain.com) with no problem.

We can't send mail to external addresses like bob@gmail.com or bob@hotmail.com. Here's an example of what I get in /var/log/mail.log

Mar 7 14:45:29 newton sm-mta[17159]: r27JjOw1017159: to=<user9999@gmail.com>, ctladdr=<root@newton.forrest> (0/0), delay=00:00:05, xdelay=00:00:05, mailer=relay, pri=30455, relay=webmail.ourdomain.ws. [xxx.xxx.xxx.xxx], dsn=5.7.1, stat=User unknown

Also, I get this:

Does that mean the user9999@gmail.com is unknown to newton, or unknown to Exchange?

Is there something in Exchange we need to configure?

I have no idea what to configure. Please help. Thanks!

Here error is from smtp , your exchange server communicating with gmail server and getting this response .

Thanks

Thanks for your reply.

I can send email to the "user9999@gmail.com" address from any other computer and the message goes through. I've also tried sending to other external (yahoo, hotmail) addresses I have and they don't go through from our Linux server. I get the same error message ("User unknown") or "unable to relay".