Sendmail エラー dsn=5.1.2, stat=Host unknown (Name server: x.x.x.x : host not found) が発生する

Issue

• メールに問題が発生し、以下のエラーが発生します。

[root@server ~]# tail -f /var/log/maillog
Oct 19 22:40:26 hostname sendmail[10411]: t9JMeQBH010409: to=<test@domain.com>, ctladdr=<root@hostname.com> (0/0), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=120536, relay=10.118.144.160, dsn=5.1.2, stat=Host unknown (Name server:10.118.144.160: host not found)
Oct 19 22:40:26 hostname sendmail[10411]: t9JMeQBH010409: t9JMeQBH010411:DSN:Host unknown (Name server:10.118.144.160: host not found)