Description of problem:
When rebooted, sendmail service fails to startup. Starting the service manually after boot works fine.

When it fails at boot, these errors show up in logs:

sendmail.service: Can't open PID file /run/sendmail.pid (yet?) after start: Operation not permitted

sm-client.service: Failed to parse PID from file /run/sm-client.pid: Invalid argument

Version-Release number of selected component (if applicable):
sendmail-8.16.1-10.el9.x86_64

Steps to Reproduce:
1. Remove postfix
2. Install sendmail (we actually do this with "-postfix" and "sendmail" in kickstart)
3. Enable sendmail and sm-client services (systemctl --enable sendmail.service sm-client.service)
4. Reboot

Actual results:
Sendmail fails to start. Sometimes with 2 start attempts (I think NetworkManager dispatch). Always with the above errors about pid files.

Expected results:
Sendmail

Additional info:
I'm able to work around this with the following in a /etc/systemd/system/sendmail.service.d/override.conf file:

[Unit]
After=network-online.target

[Service]
Restart=on-failure
RestartSec=5s
ExecStartPost=/bin/sleep 1

(ExecStartPost to sleep a second seems to be the key item, but I included the others to make sure it's after the NetworkManager stuff and restarts on failures)