[Dovecot] Converting from Maildir - sdbox

OK - I thought this was going to be easy. Maybe it is. I'm just not that good at reading directions.

Trying to use dsync. Getting this error:

Mail locations must use the same virtual mailbox hierarchy separator (specify separator for the default namespace)

Currently using maildir. The setup is as follows:

mail_uid = mail mail_gid = mail mail_location = maildir:/vhome/%d/home/%n:INDEX=/imap-cache/%d-%n

I don't have any namespace setting. Not quite sure what a namespace is or why I need one.

This is what I'm trying to run:

dsync -u marc@perkel.com backup sdbox:/email/%d/home/%n

What I'm hoping to do is do a mass conversion while running. Then shut it down - do a second quick pass - and bring it up in sdbox format.

Thanks in advance.