OK, I finally got this working!! And thanks in no small part to the folks on this list.
I disabled the virtual_alias_maps directive and corrected the virtual_mailbox_maps (which required me to also append the "/" at the end of the maildrop attributes for all of the people I needed to get mail to) as suggested and then the mail started to flow through! To think, I was about to give up and spend three grand on a mail system for only one year. This was definitely worth it. Thanks again. Regards, Christopher Koeber