The last time I tried to convert from mbox to maildir, things got pretty botched up, no data loss, but it wasn't pretty. :-)
just because you got it wrong doesn't make it's hard. you probably didn't take enough time to get it right.
Well, if you know the RIGHT way - just share it with the rest of us. I was asking Timo before and as far as I understood - there is no way of converting mbox to Maildir without losing message UIDs. And given that we already have huge mailboxes, that means that every user, connecting to the server after the conversion will need to redownload all the messages and delete all the messages in the local cache. Just imagine that user with ~5Gb of mail across 5-10 folders connect from home not-so-fast DSL line to check email and has to wait until the client rechecks all the mail.... No, this is not right. Exactly as Don Russell wrote - "no data loss, but it isn't pretty". And this is the only reason I don't migrate to Maildir. I really want to do it, but this is not something I can do to my users.
FiL