On Fri, Oct 18, 2019 at 11:32 AM, JOHN wrote:
All the messages I sent via failed to be delivered to the group.
John -- You have to send messages from an email address that is subscribed to the group. Otherwise, groups.io has no way of knowing that email came from you.
Open your activity log (Admin>Activity) and look for a log entry along the lines of "Non-member email(at)domain(dot)com attempted to send message...."
Hope this helps,
Bruce
Bruce Bowman