When stopping postgrey, the daemon logs the following warning.
This issue is referenced under debian bug report:
"Most likely the pid file should be in a directory that the user postgrey can modify (such as /var/run/postgrey/postgrey.pid) rather than /var/run/postgrey.pid, since /var/run is not writable by postgrey."
mail.warning postgrey: Couldn't unlink "/var/run/postgrey.pid" [Permission denied]
I confirmed the warnings clear with the following adjustments, However, this is not persistent as init.d needs to be updated to dynamically create the new dir.
chown postgrey:postgrey /var/run/postgrey