If you add the Email Archive tool to your site if it is not already present in the tool menu, you will be prompted for a site email address, as depicted below.

To proceed, enter a set of characters that would be valid for an email address (e.g., no spaces) and that would uniquely identify this course site. A quick way to proceed would be to paste in the site ID from your course or project site’s URL. You can identify the site ID of your course or project site’s URL as depicted below:

https://sakai.plu.edu/portal/site/SITE_ID/{etc.}

While the site email address might be used to forward a message to site participants, the message will be sent only to participants who have not set their notification preferences in the Preferences tool to opt out of receiving such emails. Consider using Announcements or Email Sender for sending emails that all site participants will receive.

The landing page of the Email Archive warns about this limitation of the site email address as depicted below.