Firstly - is it possible to mass-delete emails in Zimbra (as want to start anew). Only way I can seems to see is to go in the user's mailbox & delete in chucnks of 25's *sighs*
Secondly - The reason for the above is that I seem to have discovered a rather irritating bug in IMAPsync, where if a email has something like "Jürgen" in the FROM field, the old email server (courier) & Zimbra disagrees that both emails are actually the same (character encoding bug?). As a result IMAPSync decides to re-transfer these emails - argh.
I've fixed this hopefully by using "--useheader 'Message-ID' --skipsize", but these duplicates remains in the Zimbra mailbox, even with the --delete2 switch. This is kinda a problem for a certain mailbox, where I ran IMAPsync several times unwittingly.