In Xenforo, there is a very good Alerts feature built in.
You may have already noticed the Alerts showing at the top right of the forum.
If you hover over this, it will expend a drop down menu, showing you some of your recent alerts.
You can either click the Show All... link, or click the actual Alerts Tab to be taken to a full list of your recent alerts.
You are able to control your own alert preferences, which can be access from the drop down menu, or via Your Account page
