Write to members
In the General Administration pane, when you click this icon: you arrive on the page Write to members of your site.
Write to members :
On this page you can from this area, send a short message to all members, members of a group, a member of your site.
You select all members, group or one or more members. You type your text, then click on "Send this message"
Warning: The message will be stored in preferences: "My Mail".