| Delivered | Total emails sent minus bounces: the number of emails that were successfully delivered. |
| Unique clicks | The number of recipients that clicked on any links. The same recipient may have clicked on multiple links. This is the number of unique readers that clicked. Therefore, it's a subset of READERS or UNIQUE OPENS. |
| Clicking readers without images | Recipients that clicked on at least one link (which is why we know they opened the message), but did not download any images. |
| Total clicks | The total number of clicks. The same recipient may click on multiple links, which means that CLICKS is always larger than UNIQUE CLICKS. |
| CTOR (Click to Open Rate) | Unique clicks divided by unique opens. It's an important indicator of the quality of the message: it indicates how many of those who opened a message also clicked on one of the links it contained. |