[Dovecot] IMAP subfolders and MDBOX

[Frank Bonnet]

Hello

We actually use MBOX format on our mailhub but this
does not permit to create IMAP subfolders.
Many users are asking me fot this feature and I agree
with them of course.

My problem is to choose the format that will permit
imap subfolders creation.

Maildir is not my favorite format and I wonder about
MDBOX.

Does it permit imap subfolders creation ?
It is possible to convert from MBOX to MDBOX in one shot ?
Is it stable / mature enoug for a production server ( 4000 users ) ?

Thank you