START_IMAPD=1
START_LMTPD=1
START_SIEVE=0
START_POP3d=0
1 = start the service startup init script
0 = don't start the service with startup init script
Thank yo to :-
http://blog.benkoski.com/2008/08/ubuntus-default-dbmail-etcinitd-script/
By default DBmail in Ubuntu using sqlite. For MySQL and PostgreSQL databases you need to install different packages
For PostgreSQL
apt-get install dbmail-pgsql
For MySQL
apt-get install dbmail-mysql
Please read this
http://www.dbmail.org/dokuwiki/doku.php/setup_database