The recieving user may forward the message or reply to the message by composing a new message including part or all of the original. It maintains a record of which articles the user has read. The client displays the names for the user, and the user chooses one. The client combines the address of the document with the search terms and begins again. Otherwise, the user can choose one of the anchor elements and instruct the client to use the corresponding address for the next document.
Every document has an implicit firstpage and lastpage link destination.
Every page has an implicit link to the next and previous page. I'm formulating a model that will hopefully put all these features and objects into one framework for discussion, at least.