Re-Org / Pack
 During the message reorganisation, "holes" are left
 in the index database; about 200 Bytes per message.
 These holes are gradually re-used by new messages but
 in the event of a major clean-up deleting a lot of
 messages, a lot of wasted space could exist for a
 while. "Pack" eliminates this wasted space all at
 once.
 Packing is even slower than the message Re-Org but
 that should not be a problem, since it is seldom
 needed.