Upgrade Dovecot from 2.2.x to 2.3.x

Dovecot 2.3 breaks some backward compatible, and here's a short tutorial to convert your Dovecot 2.2 config file to fully work with Dovecot 2.3.

For more details, please read Dovecot wiki page: Upgrading Dovecot v2.2 to v2.3.

Attention

Currently only FreeBSD offers Dovecot 2.3 by the ports tree, other Linux or OpenBSD distributions still offers Dovecot 2.2, you should stick to Dovecot 2.2 if your Linux/BSD vendor doesn't offer 2.3 yet.
Dovecot 2.3 uses TLSv1 as minimal SSL protocol, if you prefer TLSv1.1 or TLSv1.2, please set the protocol version in parameter ssl_min_protocol like below:

ssl_min_protocol = TLSv1.2

Upgrade Dovecot on Linux/FreeBSD/OpenBSD

Open a shell terminal, and switch to Dovecot configuration directory first:

On Linux/OpenBSD:

cd /etc/dovecot/

On FreeBSD:

cd /usr/local/etc/dovecot/

Run commands below as root user, these commands will:

Comment out parameter ssl_protocols
Remove parameter postmaster_address
Rename plugin names and parameters:
- stats -> old_stats
- imap_status -> imap_old_stats
- stats_refresh -> old_stats_refresh
- service stats {} -> service old-stats {}
- fifo_listener stats-mail {} -> fifo_listener old-stats-mail {}
- stats_track_cmds -> old_stats_track_cmds

perl -pi -e 's/^ssl_protocols/#${1}/g' dovecot.conf
perl -pi -e 's#(postmaster_address.*)##g' dovecot.conf
perl -pi -e 's#^(mail_plugins.*) stats(.*)#${1} old_stats${2}#g' dovecot.conf
perl -pi -e 's#imap_stats#imap_old_stats#g' dovecot.conf
perl -pi -e 's#service stats#service old-stats#g' dovecot.conf
perl -pi -e 's#fifo_listener stats-mail#fifo_listener old-stats-mail#g' dovecot.conf
perl -pi -e 's#stats_refresh#old_stats_refresh#g' dovecot.conf
perl -pi -e 's#stats_track_cmds#old_stats_track_cmds#g' dovecot.conf

On RHEL/CentOS, please add new setting in dovecot.conf:

ssl_dh = </etc/pki/tls/dh2048_param.pem

On Debian/Ubuntu/OpenBSD/FreeBSD, please add new setting in dovecot.conf:

ssl_dh = </etc/ssl/dh2048_param.pem