Thanks. I'm away from my docking station at the moment and am therefore limited to using just the Axim directly.
The \Windows\Messaging folder contained 83 items, all dated 12/30/2003--presumably corresponding to the messages that were sync'd (and subsequently un-sync'd) yesterday. I ended the Inbox program, then deleted the items from the folder. The \Windows\Messaging folder is now empty, other than an empty 'attachments' folder. However, the old messages are still present in my Inbox--again, with no mail icons.
I can try this from ActiveSync tonight, but I don't expect the results to be different.