Dovecot shared folders

https://wiki.dovecot.org/ACL (Note, the configs moved from dovecot.conf)

UBUNTU 16.04:
/etc/dovecot/conf.d/10-mail.conf

# Directory where to look up mail plugins.
mail_plugin_dir = /usr/lib/dovecot/modules

# Space separated list of plugins to load for all services. Plugins specific to
# IMAP, LDA, etc. are added to this list in their own .conf files.
#mail_plugins =
mail_plugins = acl
protocol imap {
  mail_plugins = $mail_plugins imap_acl
}

https://vogasec.wordpress.com/2012/07/01/ubuntu-postfix-dovecot-shared-m...