um zu prüfen, ob gesendete Emails auch geöffnet / gelesen wurden, kann man ein hidden Pixel dazu benutzen.

1. Set-up a local environment in order to test and run the PHP script.
2. Once you've run the script, each time you open the email in your browser your IP address will be logged on the log.txt file.
3. When you're satisfied with the script, you can host the script on the server. However don't forget to change the local path of the tracking pixel to the actual URL.
4. When properly set-up each time a person opens the email, his IP-address should be logged on the log.txt file.

<img src="tracker.php?image=tracking.gif" alt="">

<img src="http://yourpath/tracker.php?image=tracking.gif" alt="">

1. You can use geo-location services like http://ip-api.com/docs/ to return the actual location of the IP-address.
2. Additionally you could use the MAPBOX API to visualize the locations on a map.

Wie das ganze genau funktioniert und den Souce Code dazu gibt es hier:

Webseite:https://github.com/brampauwelyn/php-email-tracker
download Source Code: php-email-tracker-master.zip