[Dovecot] Thunderbird and shared mailboxes

[Keith Edmunds]

I'm setting up shared mailboxes as in
http://wiki.dovecot.org/SharedMailboxes/Shared, and have set ACLs as
described on that page to share one folder of user A's mailbox with User B.

However, I'm struggling to get Thunderbird for userb at example.com to read
the shared folder of usera at example.com. Has anyone done this?

Thunderbird 3.0, Dovecot 1.2.11

Thanks,
Keith