I'm still searching for an answer to this.
After upgrade from wheezy to testing, sendmail no longer starts.
I see that the system is using systemd. I see that the /etc/init.d/sendmail script now runs /bin/systemctl start sendmail.service. But sendmail isn't started. Even running '/bin/systemctl start sendmail.service' manually, nothing happens.
I don't see any obvious way to get any debug info out of systemctl.
# systemctl is-enabled sendmail
Failed to get unit file state for sendmail.service: No such file or directory
and
# /bin/systemctl enable sendmail.service
Synchronizing state for sendmail.service with sysvinit using update-rc.d...
Executing /usr/sbin/update-rc.d sendmail defaults
Executing /usr/sbin/update-rc.d sendmail enable
# systemctl is-enabled sendmail
Failed to get unit file state for sendmail.service: No such file or directory