If you are over quota and trying to delete messages, you may find that moving messages to the Trash folder fails and you see the error message: "No free disk space. Use SHIFT+DEL to delete messages immediately bypassing the Trash folder". This is because, as a first step in the process, the message is copied to your Trash folder before it is removed from your Inbox.

To resolve this, you can go to your Trash folder and empty it of any messages already in it. Check that the folder really is empty! That may free up enough space to allow you to delete messages from Inbox, go to Trash folder and empty it.

If not, you can delete messages permanently, bypassing the Trash folder, as the error message suggests by selecting them, holding down the SHIFT key and then either pressing DELETE or clicking the delete icon in Hermes webmail.