That looks like you get turned down trying a "third-party" relay... you are apparently (from what I can see) email@example.com
(184.108.40.206), you want to send TO firstname.lastname@example.org
(220.127.116.11) but you are using a relay at 18.104.22.168. Usually the sysops disallow such a thing - you invite spam.
I don't see which mailer you use. If it's like netscape or so, just start sendmail on your machine w/o any relay (so it acts as its own mail relay), and specify "sendmail" as the mail protocol.
Where did that mail relay come from in the first place?