rhel7: nm-dispatcher: Job for sendmail.service failed because start of the service was attempted too often.

Issue

sendmail is not coming up after boot, in logs we see this:

nm-dispatcher: Dispatching action 'up' for team0
systemd: Stopping Sendmail Mail Transport Client...
systemd: Stopping Sendmail Mail Transport Agent...
systemd: Starting Sendmail Mail Transport Agent...
systemd: PID file /run/sendmail.pid not readable (yet?) after start.
systemd: Started Sendmail Mail Transport Agent.
systemd: Starting Sendmail Mail Transport Client...
systemd: Started Sendmail Mail Transport Client.
nm-dispatcher: Dispatching action 'up' for team1
systemd: Stopping Sendmail Mail Transport Client...
systemd: Stopping Sendmail Mail Transport Agent...
systemd: start request repeated too quickly for sendmail.service
systemd: Failed to start Sendmail Mail Transport Agent.
systemd: Dependency failed for Sendmail Mail Transport Client.
nm-dispatcher: Job for sendmail.service failed because start of the service was attempted too often. See "systemctl status sendmail.service" and "journalctl -xe" for details.
nm-dispatcher: To force a start use "systemctl reset-failed sendmail.service" followed by "systemctl start sendmail.service" again.
systemd: Job sm-client.service/start failed with result 'dependency'.
systemd: Unit sendmail.service entered failed state.
systemd: sendmail.service failed.