What is "Horde"?
Horde is the name of the Webmail program that we use. It is one of the best on the market and is being actively developed.
How do I permanently delete an email using Webmail?
Horde (Webmail) allows you to delete an email through the web interface. It remains on the server however until you purge deleted emails. If you delete an email, then use Outlook, the deleted emails will be downloaded since the deleted is a feature of Horde, not standard protocol. It is also possible to configure horde so it hides deleted emails. There is a Hide Deleted and Show Deleted link you can use to see deleted emails.