This is how to disable some services in controlpanel for eg Dovecot:

edit:
/usr/local/directadmin/data/admin/services.status

set dovecot, or vm-pop3d.. whichever you’re running, to “OFF”

Then disable the boot script, eg:

chkconfig dovecot off

If you want to be really sure it doesn’t start, type:

chmod 0 /etc/init.d/dovecot