When I try to delete a message from webmail it fails with: ‘There was an error deleting messages from the folder “Inbox”. This is what the server said: [TRYCREATE] Mailbox does not exist.’
Most probalby you have switched your webmail to “When deleting messages, move
them to your Trash folder instead of marking them as deleted?” in Horde IMP
preferences under “Options” -> “Deleting and Moving Messages”.
Please make sure that trash folder was created and selected under “Trash folder:” option.