I'm hearing a lot about "open time personalization" for emails, and I'm having trouble finding an explanation of how the technology actually works. The only part of an email I can think of that would be possible to change at open time would be image content. It could go like this:
- Embed some details about the recipient or other info in a query string on the image
- The user opens the email, requests the image, and the server decides what to send back based on the query string, time of day, weather, product stock levels, etc.
But, I'm seeing references that seem to point to more elaborate customization (changing which product is featured for example). How could it be possible to change the text of an email at open time? Am I missing something here or is it just fancy image swapping? How could this work with Gmail's image caching?