sendmail using localhost.localdomain
rfc2821 says that i have to use a fully qualified domain or an ip address enclosed in brackets when connecting to mail servers
how can i make sure my sendmail on linux is using an ip address instead of localhost.localdomain? and will it put it in brackets ?
i need to fix this because mail is being rejecting by some servers
[root@myhostname]# grep .*Sender.address.rejected.* /var/log/maillog
Oct 23 04:05:47 myhostname sendmail: j9MJPmF5029447: to=<email@example.com>, ctladdr=<firstname.lastname@example.org> (99/99), delay=13:39:58, xdelay=00:00:01, mailer=esmtp, pri=1291265, relay=mx.theirmailserver.com. [xx.xxx.xx.xx], dsn=4.2.0, stat=Deferred: 450 <email@example.com>: Sender address rejected: Domain not found