* Check the SSL certificate's hostname against the hostname we used
  (RFC 3501, section 11.1)

* List the available IMAP folders in the mailbox properties dialog

* Allow to set a different mail reader for each mailbox. Invoking the
  mail reader action would run the mail reader of the most recent
  message's mailbox, or fallback to the global mail reader.

* Limit the tooltip height to the screen height
