Returns an collection of mailboxes on this host. The specified
user must have at least lookup rights for each mailbox returned.
If the subscribedOnly flag is set, only mailboxes to which the
specified user is currently subscribed should be returned.
Implementations that may export circular hierarchies SHOULD restrict the
levels of hierarchy returned. The depth suggested by rfc 2683 is 20
hierarchy levels.
The reference name must be non-empty. If the mailbox name is empty,
implementations must not throw either exception but must return a single
String (described below) if the reference name specifies a local mailbox
accessible to the user and a one-character String containing the
hierarchy delimiter of the referenced namespace, otherwise.
Each String returned should be a space seperated triple of name
attributes, hierarchy delimiter and full mailbox name. The mailbox
name should include the namespace and be relative to the specified user.
RFC comments: Implementations SHOULD return quickly. They SHOULD
NOT go to excess trouble to calculate\Marked or \Unmarked status.
JAMES comment: By elimination, implementations should usually include
\Noinferiors or \Noselect, if appropriate. Also, if the reference name
and mailbox name resolve to a single local mailbox, implementations
should establish all attributes.
Note that servers cannot unilaterally remove mailboxes from the
subscribed list. A request that attempts to list a deleted, but subscribed,
mailbox must return that mailbox with the \Noselect attribute.