Sendmail Service Fails to Start Due to PID File Permission Error on Red Hat Enterprise Linux

Issue

• The Sendmail service fails to start properly on Red Hat Enterprise Linux server because it cannot write its PID file (/var/run/sendmail.pid).

  # systemctl start sendmail 
  Job for sendmail.service failed because a timeout was exceeded.
  See "systemctl status sendmail.service" and "journalctl -xe" for details.
  

• The following errors are observed in the system logs or journal output:

  May 08 12:53:08 mailserver systemd[1]: Starting Sendmail Mail Transport Agent...
  May 08 12:53:08 mailserver sendmail[40907]: unable to write pid to /var/run/sendmail.pid: Permission denied
  May 08 12:54:38 mailserver systemd[1]: sendmail.service: start operation timed out. Terminating.
  May 08 12:54:38 mailserver systemd[1]: sendmail.service: Failed with result 'timeout'.
  May 08 12:54:38 mailserver systemd[1]: Failed to start Sendmail Mail Transport Agent.