def uri_mailbox
    mb = @uri.path[1..-1]
    mb.nil? || mb.empty? ? nil : CGI.unescape(mb)
  end
def uri_mailbox
    mb = @uri.path[1..-1]
    mb.nil? || mb.empty? ? nil : CGI.unescape(mb)
  end
Gets the IMAP mailbox specified in the URI, or +nil+ if none.