This mail has been sent by the Magnolia activation Workflow.
The mail was built with a Freemarker template in which you can use variables (attributes) using the ${r"${curlyBraces}"} syntax.
In general you can use every attribute that is set on the MgnlContext (see info.magnolia.context.Context) or - in case it was sent from a workflow - attributes set on the WorkItem (see info.magnolia.module.workflow.WorkItemContext).
Furthermore, when using a workflow to send the mail you can set attributes in the WorkItemContext using the <set field="role" value="publisher"/> tag.
In most cases you might want to use the following attributes: