Control Who can Send to your Google Group
Sending Permissions
When your group is first set up, any member of the group can send out messages by e-mailing the mailing list address. If you’d like to change this, you can modify the settings to give only certain people posting permissions.
Granting Members Permission to Post
You can alter the ability of individual members of a group to post to a group. To do so, click “Members” for your group.
The members list will include a column labeled “Posting” for each member. Click the dropdown and you will see three levels of posting permissions:
'Not Allowed' means that the user cannot send emails or post to the group.
'Allowed' provides a user with unfettered access to posting to the group.
'Moderated' will allow users to attempt to email or post to the group, but will forward the content to an owner for approval via email. . Rejecting a moderated post will prevent it from being sent to the group at large, but not send notice to the individual that their post had been rejected.