When you delete an email, it is marked as a strikethrough in Horde webmail. You can set your preferences so that deleted emails are actually moved to Trash and reside there until you delete them. You can also automatically empty your Trash folder. To do so, please follow this walkthrough:
1. Goto Horde [webmail] > Settings [the sunflower icon on the menu] > Preferences > Mail
2. Go to Deleting and Moving Messages [under 'Message' section]
3. Check [*] Move deleted messages to your Trash mailbox instead of marking them as deleted in the current mailbox?
4. Click on Save.
5. After saving, two new preferences will appear.
6. Check [*] Display the "Empty Trash" link in the menubar? (Basic view only)
7. (Optional) Purge Trash how often: the default setting is "Never", that means emails will reside under the Trash folder until you manually delete them. Change the value to automatically delete messages from the trash folder.
8. Click on Save
