Read on install iredmail on debian ubuntu
1. แก้ไข Time/Zone SOGo
#chmod +w /etc/sogo/sogo.conf
#vim /etc/sogo/sogo.conf
SOGoTimeZone = "Asia/Bangkok";
#chmod -w /etc/sogo/sogo.conf
2. configure SSL
Installing TLS Certificate in Postfix and Dovecot
Ref: topic 8813-iredmail-support-timezone