Charles, Bill, Ken, thanks for the quick responses. Indeed Bill's suggestion doesn't do the trick for my configuration. Charles, I'd make your suggested change, but am concerned about Ken's further input on the topic. I don't suppose an older version of Courier-IMAP is the answer?
I'm curious.. if you have clients capable of IMAP, are they not capable of SMTP-AUTH? IMO, this is a better solution than roaming users.