"Magic phrase" is what we are calling what is more traditionally known, in terms of bars and speakeasies, as a "password," since the word "password" is already taken in computer senses to mean the secret part of a username-password credential set. So that is why it is "magic phrase" instead of "password."
Consider that you own a nightclub. Big Emet, your doorman, is to let in all your personal friends for free but charges an admission fee to strangers and others. How does your doorman identify your friends who he has not seen yet? They know the password, which for the purposes of the pay2send system we are calling the "magic phrase."
When a guest arrives and says the password (an e-mail arrives at your pay2send address containing a "magic phrase") Big Emet lets the guest in (delivers the e-mail) for free, and he remembers who it was, and why he let them in, so he can ask you who to let in immediately. These memories and your doorman asking you about them are the "magic phrase reports" that you receive whenever a magic phrase matches.
The metaphor becomes somewhat strained at this point, but the doorman is compiling a book of who gets off of which bus.
Guests who are on the "unconditional" list are allowed in regardless of which bus they arrive on. Guests on the "RAPNAP challenge" list are allowed in when they arrive on a bus that is associated with them in the doorman's book.
When someone who is on the "RAPNAP challenge" list arrives via a new bus, the doorman writes down the bus number and who the guest is on half of a three-by-five card, tears the card in half, and sends the blank half to the person. (Did you think I was kidding when I said the metaphor gets strained?) The person marks their half of the card to indicate "Yes, that is me, let me in!" or "No, that is not me, I never take that bus" and returns it to the doorman (by pneumatic tube, from their hotel) so the doorman will note in his book what to think the next time that person arrives via that bus, if it is really them or not.
RAPNAP blocks e-mails with fake return addresses. If your friends can't deal with the RAPNAP challenges, list them in the unconditional category.
David Nicol 14 Sept 2003
Be it known that any actual doormen named Big Emet are purely coincidental.