This question is related with WF Mailer Inbound.. The imap side.. The acton to be taken is in the IMAP side.. (using the imap client on the IMAP server)
Well, just do it yourself.. (Don't expect the purge actions from the apps)
Stop the mailer
Connect your imap account
Use the imap mail client's tools to delete or move messages to another folder (such as trush)
Log off your imap account(we don't want a different login other than the workflow mailer's , while it is running..)
Restart the mailer.