"Calling cards became popular at the end of the 18th century and bore the visitor's name, title and residence." (Grace, Maria. "Morning Calls and Formal Visits: Socializing in the Regency Era" English Historical Fiction Authors, http://englishhistoryauthors.blogspot.com/2013/08/morning-calls-and-formal-visits.html . Accessed 24 April 2017.) The purpose of the calling card that Willoughby leaves behind at Mrs. Jennings' residence serves to inform her, as the mistress of the house, of his presence in London. As her acquaintance, it would have been considered rude of him not to do so.

p. 11. How it is different from other things

We have tried to indicate that electronic mail is different. Part of what we mean by that is that the old telephone or letter-writing rules of behavior do not automatically transfer over to this medium and work. You don't write business letters as electronic messages; messages are usually more informal. And yet electronic messages are not printed telephone conversations either. What we find is that the medium is different enough, and the average user's experience has been short enough, that problems arise. Meanings are misunderstood. Tempers flare and cause ill-conceived responses to be written. Many recipients' time is wasted reading content-free or irrelevant messages.

What we need is a new set of rules: how to be a constructive, courteous sender and receiver or electronic messages. We certainly do not have this set of rules, all tied up in a tidy package. We do, however, feel it is important to hasten the cultural evolution toward this goal. What follows, then, is a discussion of some of the important guidelines we've observed from experience.