Thanks for the response.
I had already found that document online, but like you said, it makes no mention of the from: and to: syntax, so it does me no good in this case.
I know that my current setup does work, however. In the past, when I've needed to accept mail from this domain to our "all" address, I simply commented out that line and the mail came through fine.
EDIT - I also found http://www.sendmail.org/m4/anti_spam...access_db_fine
that discusses the "from" amd "to" tags, but I don't really understand how to do what I'm proposing.
Anyone else have a suggestion?