how to debug what happens inside mailboxes

[Martin Kraus]

Hello. 
  I'm using cyrus 2.3.14 on a mailserver and a few users are complaining, that
sometimes a message gets deleted from the mailbox after reading it. They are
using some sort of outlook. Users are using imap to connect to their
mailboxes. Is there a way to debug imap communication between outlook and
cyrus imapd other then using tcpdump?

Thanks
Martin Kraus