Thank you for reply.

A namespace will contain multiple mailboxes. Typically you'd have several mailboxes created under /home/share/Maildir, such as:

/home/share/Maildir/.First shared box/ /home/share/Maildir/.Second shared box/

...

Thunderbird can see "share" , but can't subscribe.....

That's because "share" is a namespace prefix and not a mailbox.

I setup this and Thunderbird see share . But, show permission problem.......

I set up all permission to shared Maildir, # chmod -R 777 /home/share/Maildir

but, many permission trouble wake up............... I can't know what happen....

In courier-imap, I set up only 3 step.

1. create maildir

maildirmake -S /home/shared

2. create maildirshared file

echo 'SHARE /home/shared ' > /etc/courier/maildirshared

(use tabcode)

3. edit imapd config file IMAP_UMASK=022 IMAP_SHAREDINDEXFILE=/etc/courier/shared/index

Is there way like this on dovecot ?