A client was trying to delete messages from their mailbox using Horde webmail on a Plesk linux system. They received the following error:
There was an error deleting messages from the folder “Inbox”. This is what the server said: [TRYCREATE] Mailbox does not exist.
Turns out that they had enabled a setting in the “Options->Deleting and Moving Messages” area which was:
When deleting messages, move them to your Trash folder instead of marking them as deleted?
Disabling this setting allowed delete to work again fine.