I tried to send a mail to firstname.lastname@example.org, but got the following message:
We're writing to let you know that the group you tried to
contact (mobile) may not exist, or you may not have permission to post messages
to the group. A few more details on why you weren't able to post:
* You might have
spelled or formatted the group name incorrectly.
* The owner of the group may have removed this group.
* You may need to join the group before receiving permission to post.
* This group may not be open to posting.
If you have questions related to this or any other Google Group, visit the Help Center at https://support.google.com/a/moodle.com/bin/topic.py?topic=25838.