We developed an email service that supports the progressive propagation of images embedded in or attached to emails. On the sender side, the progressive email services use Outlook's email client to generate emails. On the receiving end, we support both CoFi-enabled clients running Outlook and standard third-party email readers.
We implemented emails as CoFi shared documents that are written only by the email's sender but are read by one or more recipients. Our sender adaptation policy propagates the text content of new emails, transcodes images into a progressive JPEG representation and sends only portions of an image's data. The sender can propagate fidelity refinements for images by selecting the email from a special Outlook folder and re-sending it. The image fidelity refinements are available to CoFi-enabled recipients as soon as they reach the CoFi remote proxy. For CoFi-enabled recipients, our adaptation policy fetches the email's text content and transcoded versions of its image attachments. Readers request fidelity refinements by clicking a refresh button added on Outlook's toolbar. Finally, we support third-party email readers by composing a new email message once all images have reached full fidelity.