This describes how your users can use the Mail Page plugin to share content even with people that are not registered Confluence users.
Sharing a page
Sharing a page works via the Send page link in the top right corner of your page.
You will be presented with a dialog where you can choose users from your Confluence, enter any email address you like or share the page with a whole user group. Users and groups can be chosen from a drop down, email addresses have to be confirmed with a click on the + add link. If you chose a wrong user, email or group, you can delete it with a click on the x.