Our apologies, the image you referenced contains misleading info, and has been removed from the documentation. I am sorry for the misunderstanding and inconvenience.
As you probably know, the Discovery module (an example of which is accessible via http://epadd.stanford.edu) provides a redacted view of messages, including message headers, and is intended to provide a way to surface these materials online while protecting privacy/copyright and related concerns.
The Delivery module, on the other hand, provides full access to all messages and attachments that have not been marked "restrict" or "do not transfer." There is currently know way to redact parts of correspondent addresses or messages in the Delivery module.
This use case has not yet come up, and we would be glad to learn if having that option available would be helpful for your institution. Otherwise, apologies again for the confusion.
Many thanks for your feedback,