What Factors may Affect Email Load Time?

Internal Factors

Email Content: One of the major factors that can play a significant role in email load time, is the size and complexity of the email content. Emails with large images, videos, or attachments will take longer to load. Optimizing images and using efficient file formats can help reduce load times. Emails should be designed to be responsive, meaning they adapt to different screen sizes and devices. Poorly designed emails may load slowly on mobile devices.
Email Server Performance: In case if the email server hosting is slow or experiencing high traffic, it can result in delayed email loading times.

Internet Connection: The recipient's internet connection speed can affect email load times. A slow or unstable internet connection will cause emails to load more slowly, especially if they contain rich media.
Browser Compatibility: If the email is being viewed in a web-based email client, the compatibility of the email with different web browsers can affect load times. It's essential to test emails in multiple browsers to ensure they load quickly and correctly.
Email Client: The email client being used to access the email can impact load times. Some email clients may be more efficient at rendering emails than others, leading to variations in load times.
Load times may vary from user to user based on the cache availability as well. It can help speed up email load times for recipients who have previously opened emails from the same sender. However, if these cached elements are not available or have expired, it can slow down load times.