I’ve run into this issue a couple of times now so I’m assuming others are as well. Servers set up on Amazon EC2 with default sendmail configuration seem to get the following error in their /var/log/maillog:
12 Sep 19 19:48:26 DOMAIN sendmail[31192]: q8JJmQQV031192: ... User unknown 13 Sep 19 19:48:26 DOMAIN sendmail[31191]: q8JJmQ0D031191: [email protected], ctladdr=DOMAIN.com (504/502), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30695, relay=[127.0.0.1] [127.0.0.1], dsn=5.1.1, stat=User unknow 14 Sep 19 19:48:26 DOMAIN sendmail[31192]: q8JJmQQV031192: from=, size=695, class=0, nrcpts=0, proto=ESMTP, daemon=MTA, relay=localhost [127.0.0.1] 15 Sep 19 19:48:26 DOMAIN sendmail[31191]: q8JJmQ0D031191: q8JJmQ0E031191: DSN: User unknown 16 Sep 19 19:48:26 DOMAIN sendmail[31192]: q8JJmQQX031192: from=<>, size=2616, class=0, nrcpts=1, msgid=, proto=ESMTP, daemon=MTA, relay=localhost [127.0.0.1] 17 Sep 19 19:48:26 DOMAIN sendmail[31191]: q8JJmQ0E031191: to=DOMAIN.com, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=31719, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (q8JJmQQX031192 Message accepted for delivery) 20 Sep 19 19:48:26 DOMAIN sendmail[31193]: q8JJmQQX031192: to=, delay=00:00:00, xdelay=00:00:00, mailer=local, pri=32817, dsn=2.0.0, stat=Sent 21 Sep 19 19:49:36 DOMAIN sendmail[31200]: q8JJnaxi031200: from=DOMAIN.com, size=698, class=0, nrcpts=1, msgid=, relay=DOMAIN.com@localhost
The solution that I have found to work is to modify /etc/mail/sendmail.mc and add the following to the very end:
define(`MAIL_HUB', `DOMAIN.com.')dnl define(`LOCAL_RELAY', `DOMAIN.com.')dnl
Be sure to replace DOMAIN with your local domain.
Notice: The above define code entries start with a ` and end with a ‘. Make sure you copy+paste the above as it is, and modify the domain as it’s not the standard begin with a ` and end with a `.
After doing so, you’ll need to install sendmail-cf and run a reconfiguration with the following:
cd /etc/mail/ yum install sendmail-cf /etc/mail/make
Lastly, restart sendmail:
service sendmail restart
Hi Beshoy – just wanted to say thanks for this article. I was getting the ‘unknown user’ issue on my linux VM due to the same email routing problem. I read a LOT of forum posts on the issue, but it was your information that actually worked.
Thanks again!
Thanks, it worked for me
Thanks, worked perfectly after much head scratching!
Thank you, thank you, thank you! After hours of searching and reading countless misleading ‘solutions’ this one worked!!