You need to scan entry page for links, filter out outbound links, then follow every link. Each page you visit you need to scan for general email pattern. It should handle all simple cases. If you will use headless browser you can also grab emails that rendered on page using JS. If there are emails on images, you can also attach OCR functionality.
Don't forget to check out for more tutorials! I hope this article helps you understand the differences between one click scraping and web scraping as well as the different types of scraping that are out there.