Update 2014.02.19

This update solves an issue with the message IDs which are (surprisingly for me) NOT univocal: if you delete a message from your IMAP folder, the next new incoming message will take the ID of the just deleted one.
Anyway, now the MSGS_ID List<> (responsible for notifying only one time each unread message) will record a custom uniqueID created with message date and sender (string UNIQUE_ID = msg.Date.ToString() + msg.From.ToString();).