I have a closed google group that I administrate as the only owner. Only members are allowed to send email to this group. For purposes of this example, let's say it's called "my-group". Normal users receive mail that says it is from
email@example.com when a group member sends mail to the group address.
Recently the group spam filter has filtered many messages purporting to be from
firstname.lastname@example.org. This is the spam filter for the google group, not the spam filter for my email account. This address is not a member of the group; it is the group address. Can this address be safely blocking without breaking normal group usage? Or is there another way to prevent messages that are not from the group from getting to the group spam filter?