Javadoc
Renames an existing MailBox. The specified mailbox must already
exist locally, the requested name must not exist locally already but
must be able to be created locally and the user must have rights to
delete the existing mailbox and create a mailbox with the new name.
Any inferior hierarchical names must also be renamed.
If INBOX is renamed, the contents of INBOX are transferred to a new
folder with the new name, but INBOX is not deleted. If INBOX has
inferior mailboxes these are not renamed.
It is an error to create a mailbox with the name of a mailbox that has
been deleted, if that name is still in use.