Migrating from maildir to mdbox

Hi everybody,

I have a virtual user setup that is using maildir, and I'd like to migrate it to mdbox. Following directions from 

	http://wiki2.dovecot.org/Migration/MailFormat

and keeping in mind that my maildir is in  maildir:/mnt/vmail/%d/%u, after having updated 10-mail.conf I have tried to execute:

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

But it replies this answer, that I do not understand:

	dsync(user@domain.org): Error: Mail locations must use the same virtual mailbox hierarchy separator (specify separator for the default namespace)

What am I doing wrong?

Thank you,
Felix