Milter-greylist

Hello,

I see in 3.1.4 ChangeLog:
Add support for switching to a given group

What does it mean?

A (possibly related?) problem - milter-greylist is running as user smmsp,
and I added postfix user to group smmsp. I need to execute the following
command after starting milter-greylist:
chmod g+w /var/milter-greylist/milter-greylist.sock
so that postfix could write to the socket. Is it possible to use some config
file option or smth instead of running chmod?

Regards,
Nerijus