The fedora package uses a FHS compliant directory layout and does NOT
place files below /var/milter-greylist. Instead:
* the database is located at /var/lib/milter-greylist/db
* the sendmail socket is located at /var/run/milter-greylist/milter-greylist.sock
* the pidfile is located at /var/run/milter-greylist.pid
This might be incompatible with online documentation that refers to
the original paths. Hence, please use the documentation provided by
this package where you should find actual paths.
You might need to give 0666 permissions to the socket file:
| socket "/var/run/milter-greylist/milter-greylist.sock" 0666
Alternatively, use a TCP socket and setup iptables rules to allow only
connections from the postfix user.