Sent items folder

How is Usermin's Read Mail module determining the Sent items folder location? I have the "Sent mail folder file" in the module config set to Automatic, and instead of picking up the existing Maildir/.Sent folder, it's linking it to the entirely nonexistent Maildir/.sentitems. Interestingly, it's getting Maildir/.Drafts just fine with the same Automatic setting.

Does it just guess at common folder names, or is it inheriting this config from somewhere else in my VMPro setup?