If the status code for this response is one of:
ARTICLE_FOLLOWS
HEAD_FOLLOWS
BODY_FOLLOWS
then this stream can be used to retrieve the byte content of the article
retrieved.
If true: the mailbox has been marked "interesting" by the server;
the mailbox probably contains messages that have been added since
the last time the mailbox was selected.
If true: it is not possible for any child levels of hierarchy to
exist under this name; no child levels exist now and none can be
created in the future.