Hi Cliff,
Welcome aboard.
I'm no expert, but in my brief experiences with sendmail I learned that it was something to be avoided if possible. Anything that required configuration files to be edited with a tab-preserving editor seemed rather too-unfriendly to me. :-)
Have you looked at [link|http://www.courier-mta.org/|Courier] once recommended by Static, and [link|http://www.qmail.org/top.html|qmail] once recommended by broomberg? I haven't tried either of them myself.
Sendmail is pretty hard to diagnose without seeing the configuration file. If you still want to go with it, you might need to post the changes you made (suitably obsfuscated) for someone (not me) to be able to help.
Best of luck. HTH.
Cheers,
Scott.