Lazy loading in emails typically involves using JavaScript to detect when an image or other resource comes into the viewport, and then dynamically load the resource. However, it's important to note that not all email clients support JavaScript. Therefore, the implementation can vary:
CSS Techniques: Use CSS to create placeholders for images and other content that loads as the user scrolls. Progressive Enhancement: Ensure that your emails work without lazy loading for clients that do not support it, while offering enhanced performance for those that do.