Oracle Linux: Sending Email via "mail" Command With Sendmail Fails With Error "stat=Deferred: Name server: xxxxx: host name lookup failure" (Doc ID 2774022.1)

Last updated on MAY 06, 2021

Applies to:

Symptoms

Sending email via mail command fails with below error:

[root@server ~]# echo "Email testing at 'date'" | mailx -v -r "user@domain.com" -s "Testing from 'hostname'" user@domain.com;tail -f /var/log/maillog user@domain.com... Connecting to [127.0.0.1] via relay...
220 mail ESMTP server ready at Thu, 11 Mar 2021 14:46:12 -0500
>>> EHLO server.domain.com
250-server.domain.com Hello localhost.localdomain [127.0.0.1], pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250-SIZE
250-DSN
250-ETRN
250-AUTH GSSAPI
250-DELIVERBY
250
Mar 11 14:37:56 server sendmail[371339]: 129J3vCA082646: to=<user@domain.com>, delay=2+00:31:59, xdelay=00:00:00, mailer=relay, pri=4621773, relay=smtp.server.com, dsn=4.0.0, stat=Deferred: Name server: smtp.server.com: host name lookup failure
Mar 11 14:37:56 server sendmail[371339]: 129EeaY8125513: to=<user@domain.com>, delay=2+04:57:20, xdelay=00:00:00, mailer=relay, pri=5160535, relay=smtp.server.com, dsn=4.0.0, stat=Deferred: Name server: smtp.server.com: host name lookup failure
Mar 11 14:37:56 server sendmail[371339]: 129EkNC8214520: to=<user@domain.com>, delay=2+04:51:33, xdelay=00:00:00, mailer=relay, pri=5160535, relay=smtp.server.com, dsn=4.0.0, stat=Deferred: Name server: smtp.server.com: host name lookup failure
Mar 11 14:46:12 server sendmail[96755]: 12BJkBEd096755: from=user@domain.com, size=376, class="0", nrcpts=1, msgid=<604a7383.Fhi903gkKraq+37o%user@domain.com>, relay=root@localhost
Mar 11 14:46:12 server sendmail[96758]: 12BJkC3i096758: from=<user@domain.com>, size=536, class="0", nrcpts=1, msgid=<604a7383.Fhi903gkKraq+37o%user@domain.com>, proto=ESMTP, daemon=MTA, relay=localhost.localdomain [127.0.0.1]
Mar 11 14:46:12 server sendmail[96755]: 12BJkBEd096755: to=user@domain.com, ctladdr=user@domain.com (0/0), delay=00:00:01, xdelay=00:00:00, mailer=relay, pri=30376, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (12BJkC3i096758 Message accepted for delivery)
Mar 11 14:46:12 server sendmail[96880]: 12BJkC3i096758: to=<user@domain.com>, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=120536, relay=smtp.server.com, dsn=4.0.0, stat=Deferred: Name server: smtp.server.com: host name lookup failure

Cause

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