When you use the Share button to share a Postwire, we generate a special link for each recipient. If you invite 10 people, we generate 10 unique links to the same Postwire. Therefore, when a person clicks on his or her unique link, we can tell you exactly who viewed your Postwire.
When you copy and paste the link to a Postwire from your browser address bar--or when you use the Outlook or Gmail plugins--we have no way of tracking exactly who clicks to view your Postwire. In these situations, we want to give you some intelligence, so we show you the viewer's company domain or ISP and location that's reported to us using reverse IP lookup.