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Old 03-07-2013, 03:12 PM   #1
Registered: Jul 2012
Posts: 37

Rep: Reputation: Disabled
dsn=5.7.1, stat=User unknown

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, the server can send mail to with no problem.

We can't send mail to external addresses like or 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=<root@newton.forrest> (0/0), delay=00:00:05, xdelay=00:00:05, mailer=relay, pri=30455, [], dsn=5.7.1, stat=User unknown

Also, I get this:

root@newton:/etc/mail# sendmail -bv deliverable: mailer relay, host, user
Does that mean the 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!
Old 03-08-2013, 09:34 AM   #2
Registered: Feb 2008
Distribution: Fedora,RHEL,Ubuntu
Posts: 661

Rep: Reputation: 66
Here error is from smtp , your exchange server communicating with gmail server and getting this response .

Old 03-08-2013, 10:15 AM   #3
Registered: Jul 2012
Posts: 37

Original Poster
Rep: Reputation: Disabled
Thanks for your reply.

I can send email to the "" 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".


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