Here is my solution for WP exit popup and I have included files for the job get done
Here is situation there is 2 files in two folders atached in zip file.
1.
exit.php goes to the template folder
2.
pop.htm goes to the root of the WP
Go to Manage and create PAGE (not post) name the page and scroll down and choose Exit-Popup template and hit publish.
Preview it and modify html contents in both files as you like. Good luck.