The accountprune program that comes with MDaemon can do this. Create a midnight.bat file and place it in the MDaemon\app directory.

For the contents, enter:

Accountprune /m /d=2 /p=''Spam.IMAP''

The midnight.bat is run every night at midnight.

In older versions of MDaemon (v8 and previous) the spam folder was called ''Junk E-mail.IMAP''.