* Each message's metadata now has the ability to cache the length of

* Each message's metadata now has the ability to cache the length of
  the message when output in RFC822 format.  The POP3 service populates
  this field the first time it sees each message, and fetches the length
  from cache on subsequent visits.
* Because of this optimization, we no longer need to keep the entire POP3
  mailbox stored in open temp files during a session.  Each message is
  opened again when it is fetched.