You can. Create a new topic by sending an email to the address assigned to that group’s discussion forum. To get that email address, visit the group’s discussion forum and click on the “Create New Topic” button . 

Click on the link beside “Did you know you can post new topics to this group from your email client?” Another text box will appear with the email address that you can use to post new topics by email. 

The message must be sent from the email account associated with your Commons account. The subject of the email will become the title of the discussion topic.