Thanks. I was able to close two of the data files. I am unsure of what you are suggesting that I do about the third one. I just want messages sent from the third email address to appear under Sent in the default file and not have to keep this other data file open.

If I follow your directions and go to File>Infor>Account Settings and pick the "Email" tab, I can see that it is using a different data file (though in practice it seems to be using that file's Sent box only). If I try to change the Delivery Email Location, the only options I see are the Inbox for the current file (though Outlook is actually delivering them to the default file's Inbox) and no option to pick the only other data file displayed (which apparently is called "Data File").

Not sure what to do with this, other than change it to Data File and see what happens.