Migrating from maildir to mdbox

Hi all,

I have (I think) migrated my dovecot mail format from maildir to mdbox. I have changed in 10-mail.conf the format from maildir to mdbox, and I have executed this command for all my users:

dsync -u user@domain.org mirror maildir:/mnt/vmail/domain/user

The only output of the command has been, for some users, this:

dsync(user@domain.org): Warning: quota: Namespace '' is not Maildir, skipping for Maildir++ quota

Is this important? How can I check that I am effectively using the new format?

Thank you,
Felix