Problem with mail rate limiting

Hello,

This is my first post on this forum.

I have problem with mail rate limiting feature of Virtualmin. When I set the rate limit I get this message:

=====
Starting milter-greylist server ..
.. startup failed : Starting milter-greylist (via systemctl): Job for milter-greylist.service failed because a configured resource limit was exceeded. See "systemctl status milter-greylist.service" and "journalctl -xe" for details. FAIL
====

if I run command systemctl status milter-greylist.service a root I see this:

=====
milter-greylist.service - SYSV: Milter Greylist Daemon
Loaded: loaded (/etc/rc.d/init.d/milter-greylist)
Active: failed (Result: resources) since lun 2016-02-15 12:48:55 CET; 1min 37s ago
Docs: man:systemd-sysv-generator(8)
Process: 9168 ExecStart=/etc/rc.d/init.d/milter-greylist start (code=exited, status=0/SUCCESS)

feb 15 12:48:55 systemd[1]: Starting SYSV: Milter Greylist Daemon...
feb 15 12:48:55 milter-greylist[9170]: cannot read dumpfile "/var/lib/milter-greylist/db/greylist.db"
feb 15 12:48:55 milter-greylist[9170]: starting with an empty greylist
feb 15 12:48:55 milter-greylist[9168]: [43B blob data]
feb 15 12:48:55 systemd[1]: PID 9171 read from file /var/run/milter-greylist.pid does not exist or is a zombie.
feb 15 12:48:55 systemd[1]: Failed to start SYSV: Milter Greylist Daemon.
feb 15 12:48:55 systemd[1]: Unit milter-greylist.service entered failed state.
feb 15 12:48:55 systemd[1]: milter-greylist.service failed.
=====

any idea how to fix it?.

Regards.