Overlay
Overlay is a technique that allows adding additional information to visual material (such as a website, a video or, in this context, a newsletter).
In Laposta, you will find an overlay of each sent newsletter on the page Results → Links → Overlay. This overlay provides a full view of your newsletter, showing for each link how many subscribers clicked on it and how often they did so collectively.
The number of clicks on the various links in your newsletter is, so to speak, visualised with an overlay.
Laposta cannot measure the number of clicks on a mailto link. A mailto link opens a mail programme on the computer of your subscriber. Laposta is not a part of this process. (We can allow normal links to pass through our servers, but not mailto links).