there is no init script for calling mailmanctl to start mailman after booting Reproducible: Always Steps to Reproduce:
Which version are you using ? There is an rc file that's installed as /etc/init.d/mailman in all ebuilds I see available (I rsync'd today), the versions are: 2.1.1-r2, 2.1.1-r3, 2.1.2-r1, 2.1.2.
there is an init script in every version.