I've had similar problems jastanle84 and I don't even need sendmail. But I never could seem to get rid of it, even disabling the service did not help.
What can get rid of the error message though is modifying your /etc/hosts file.
Remember, each host can have several aliases. They are just listed on the same line, like this:
w.x.y.z myhost mycrazyhost mywackyhost
(Of course the w-z are replaced by numbers. That is your IP address.) "So what?" you say? Big deal, I can use several names for the same machine. Uh-huh it is a big deal if you want to get rid of this error message. The "domain name" it is looking for is anything after the host name and a dot, so you can do something like this:
111.222.333.444 myhost myhost.quiet
That's all there is to it. Oh, you might have to stop/restart sendmail or even the inet daemon (or reboot if you can). I forget, but I think you might not have to do this. Try it and let everyone know.