Trying to configure sendmail in Debian

raphael75

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=, ctladdr= (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

Sometimes it says stat=Unable to relay and sometimes stat=Sent, but in every case the emails are never received.

Also, I get this:

root@newton:/etc/mail# sendmail -bv user9999@gmail.com

user9999@gmail.com... deliverable: mailer relay, host webmail.ourdomain.ws, user user9999@gmail.com

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!