Teach Horde to use the Trash can

Go to your inbox, click Options at the top.

Choose "Deleting and Moving Messages" (in the middle).

Put a check mark by the option "When deleting messages, move them to your Trash folder instead of marking them as deleted?"

Under "Trash folder:" select Create a new trash folder

Give it the name Trash and hit OK

Click Save Options

Next time you login the Trash folder will appear.