Oh thats funny ! this is the #1 reason I switched from UW-IMAP TO Dovecot so I could put mail in ~/Mail WITHOUT having to set the Root Folder option on the client ... too many people (well everyone, even the ones I told how to do it right) were getting it wrong and would switch mail clients and forget to add ~/Mail or use ~/mail or ~\Mail or ~Mail\ or various other bastardazations and leave mailboxes all over ...

Thank you Timo for doing this one RIGHT ... (that is, let me configure it).

Oh the other thing I discovered, probably obvious to everyone else but not to me at first. Those INDEX files ... they really confused some mail programs like squirrelmail ... and my PPC IMAP client. so I put them somwhere else :INDEX=/var/spool/mailindex/%u very nice feature

would it be possible not to treat ~/mail specially and not to add mailboxes in the directory automatically? It would make migrating from IMAP-UW easier.

Well, how about:

default_mail_env = mbox:%h:INBOX=/var/mail/%u

That should make it compatible with UW-IMAP.