[Dovecot] create Sub-Subfolders

[Jon]

Setting up namespaces like this on an ubuntu maverick server HAS accomplished
allowing sendmail to deliver email to /var/mail/jon in mbox format and then,
using a thunderbird client from another machine, drag email's to Maildir type
folders in ~/Maildir on that remote server.

My question is, once a file is DELETED, or moved out of the inbox folder (at
least as seen by thunderbird), the file IS copied to the correct Maildir folder,
HOWEVER, that email STILL resides in /var/mail/jon.  No longer shows up in my
inbox folder on thunderbird (presumably because it has been indexed around), but
it is still there.  This means that /var/mail/jon is going to grow everytime I
get an email and NEVER shrink.

Am I doing something wrong that dovecot is doing a COPY instead of a move, or is
it some silly Thunderbird setting?

jon