Dovecot 2.3 changes - Notice for upgrades from Version 2.2 to Version 2.3
These are the new configuration commands:
recipient_delimiter is now an alternative delimiter characters
director_doveadm_port setting removed. Name the inet_listener doveadm { .. } instead.
mdbox_purge_preserve_alt removed.
ssl_protocols setting replaced by ssl_min_protocol. Now you only specify the minimum ssl protocol version Dovecot accepts, defaulting to TLSv1.
ssl_parameters replaced with ssl_dh. SSLv2 is not supported in ssl_protocols.
director_consistent_hashing removed