[ubuntu] spam assassin won't start after upgrade from 14.04 to 16.04.1

After the upgrade, a few of my services would not start at boot. ntp, courier-authdaemon and spamassassin. I was able to get ntp and courier-authdaemon migrated to systemd, and now those start at boot. But spamassassin can only be manually started. I looked around the 'net for migration instructions, but was not able to find anything, so I'm tuing to you folks. What do I need to do the get spamassassin starting at boot.
Thanks