This option allows You to purge folder by deleting all it's content immediately. To do that:
- login into your account,
- open section "Options"
- from the menu on the left choose "Folders",
- in a folder list choose the folder You want to purge and click on the icon besides this folder,
- approve your choise - press "OK" - and all the content from this folder will be deleted.
If you were unable to find answer for your question, please write to firstname.lastname@example.org