[Dovecot] Problem deleting folders with Thunderbird?

[Knute Johnson]

I am running Thunderbird 2.0.0.14 on Windows XP.  When I try to delete 
one of the folders I get a dialog with the following "The current 
command did not succeed.  The mail server responded: Target mailbox 
doesn't allow inferior mailboxes."  I am running dovecot version 
1.0.13-6.fc8 under Fedora 8.  The output of dovecot -n is below;

[root at www knute]# dovecot -n
# 1.0.13: /etc/dovecot.conf
protocols: imaps pop3s
disable_plaintext_auth: yes
login_dir: /var/run/dovecot/login
login_executable(default): /usr/libexec/dovecot/imap-login
login_executable(imap): /usr/libexec/dovecot/imap-login
login_executable(pop3): /usr/libexec/dovecot/pop3-login
mail_executable(default): /usr/libexec/dovecot/imap
mail_executable(imap): /usr/libexec/dovecot/imap
mail_executable(pop3): /usr/libexec/dovecot/pop3
mail_plugin_dir(default): /usr/lib/dovecot/imap
mail_plugin_dir(imap): /usr/lib/dovecot/imap
mail_plugin_dir(pop3): /usr/lib/dovecot/pop3
auth default:
   passdb:
     driver: pam
   userdb:
     driver: passwd

Is there something to be configured to allow mail box deletion?  I know 
there was a similar discussion this week about users deleting their 
mailboxes accidentally.  Are folders within folders allowed by dovecot?

Thanks very much,

-- 

Knute Johnson
linux at www.knutejohnson.com