Steps to follow for purge delete.
- Horde > Preferences > Mail > Deleting and Moving Messages.
- Tick the second checkbox “Move deleted messages to your trash mailbox instead of marking them as deleted in the current mailbox?”
- Save the changes.
- Select trash mailbox as deleted items.
- Tick the checkbox “Display the empty trash link in the menu bar?”
- Save the changes.
For your assistance you can visit the following link.
https://www.youtube.com/watch?v=UmpiODpyyFk