"User not found" - Unable to send mail to domain

Installing, Configuring, Troubleshooting server daemons such as Web and Mail
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ivanh
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"User not found" - Unable to send mail to domain

Post by ivanh » 2015/06/18 18:53:52

Hello,

I have two nearly identical servers running CentOS 5.11. I am unable to send mail to one particular domain on Office365 from one of them but am still able to send mail to my gmail account. Searching through maillog, all other emails seem to be sent fine. I'm using the command line mail program like so:

echo 'testing' | mail -s "test test " xxx@xxxx.com -- -f xxx@xxxx.com

Here are the contents of maillog for the failed request:

Jun 18 14:45:49 ip-172-31-33-236 sendmail[8863]: t5IIjnAL008863: from=xxx@xxxx.com, size=68, class=0, nrcpts=1, msgid=<201506181845.t5IIjnAL008863@localhost.localdomain>, relay=root@localhost
Jun 18 14:45:49 ip-172-31-33-236 sendmail[8864]: t5IIjnMZ008864: from=<xxx@xxxx.com>, size=374, class=0, nrcpts=1, msgid=<201506181845.t5IIjnAL008863@localhost.localdomain>, proto=ESMTP, daemon=MTA, relay=v4prod [127.0.0.1]
Jun 18 14:45:49 ip-172-31-33-236 sendmail[8863]: t5IIjnAL008863: to=xxx@xxxx.com, ctladdr=xxx@xxxx.com (0/0), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30068, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (t5IIjnMZ008864 Message accepted for delivery)
Jun 18 14:45:50 ip-172-31-33-236 sendmail[8866]: STARTTLS=client, relay=xxx.mail.protection.outlook.com., version=TLSv1/SSLv3, verify=FAIL, cipher=AES256-SHA, bits=256/256
Jun 18 14:45:55 ip-172-31-33-236 sendmail[8866]: t5IIjnMZ008864: to=<xxx@xxxx.com>, delay=00:00:06, xdelay=00:00:06, mailer=esmtp, pri=120374, relay=xxx-c...ction.outlook.com. [207.46.163.138], dsn=5.7.1, stat=User unknown

Here's the maillog results from the server that isn't having any issues:

Jun 18 15:18:34 awsv4dev sendmail[16487]: t5IJIYr7016487: from=xxx@xxxx.com, size=61, class=0, nrcpts=1, msgid=<201506181918.t5IJIYr7016487@localhost.localdomain>, relay=root@localhost
Jun 18 15:18:34 awsv4dev sendmail[16488]: t5IJIYir016488: from=<xxx@xxxx.com>, size=367, class=0, nrcpts=1, msgid=<201506181918.t5IJIYr7016487@localhost.localdomain>, proto=ESMTP, daemon=MTA, relay=awsv4dev [127.0.0.1]
Jun 18 15:18:34 awsv4dev sendmail[16487]: t5IJIYr7016487: to=xxx@xxxx.com, ctladdr=xxx@xxxx.com (0/0), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30061, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (t5IJIYir016488 Message accepted for delivery)
Jun 18 15:18:35 awsv4dev sendmail[16490]: STARTTLS=client, relay=xxxx.mail.protection.outlook.com., version=TLSv1/SSLv3, verify=FAIL, cipher=AES256-SHA, bits=256/256
Jun 18 15:18:37 awsv4dev sendmail[16490]: t5IJIYir016488: to=<xxx@xxxx.com>, delay=00:00:03, xdelay=00:00:03, mailer=esmtp, pri=120367, relay=xxxx-c...ction.outlook.com. [207.46.163.215], dsn=2.0.0, stat=Sent (<201506181918.t5IJIYr7016487@localhost.localdomain> [InternalId=11849814770907, Hostname=BLUPR11MB0436.namprd11.prod.outlook.com] Queued mail for delivery)

Sendmail is 8.13.8-10.el5_11 on both servers.

Any Ideas? That only thing I can see is the hostname in maillog "ip-172-31-33-236" is not the hostname of my machine. I updated both /etc/hosts and /etc/sysconfig/network with the name that is specified in relay.

Thanks!

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TrevorH
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Re: "User not found" - Unable to send mail to domain

Post by TrevorH » 2015/06/18 19:41:18

If the remote end replies "User Unknown" then it's not your problem, it's theirs.
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ivanh
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Joined: 2015/06/18 18:23:21

Re: "User not found" - Unable to send mail to domain

Post by ivanh » 2015/06/19 14:21:58

Hmm, that makes sense. A couple of questions though:

1. What can I do to resolve the problem? The email does exist and works fine in Office365 as well as when connecting from my mail client.
2. Why does it work fine from the other server?

Thanks!

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TrevorH
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Re: "User not found" - Unable to send mail to domain

Post by TrevorH » 2015/06/19 18:57:09

Since you obscured the only useful information in the logs, that's a question only you can answer.
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