http://tumbleweed.org.za/2007/10/03/dovecot-shared-mailboxes-correct-way
http://www.cbjck.de/2013/06/22/setting-up-shared-mailboxes-in-dovecot/
http://switzernet.com/3/public/131212-shared-imap-dovecot/index.pdf
http://www.iredmail.org/forum/topic358-iredmail-support-how-create-public-shared-folder-with-dovecot.html