Several factors can affect the Speed Index of an email:
Image Optimization: Large or unoptimized images can slow down the loading time. Using optimized images and proper formats can significantly improve the Speed Index. Code Efficiency: Clean and efficient HTML and CSS code can enhance the loading speed of an email. Server Response Time: The speed at which the email server responds can also impact the Speed Index. Third-Party Content: Embedding content from third-party sources can slow down the email load time.