Where a message lands depends on who sent it. Mail from people in your contacts goes to the Inbox. Mail from strangers waits in Unknown Senders, where Add to Contacts... makes a stranger a contact. Bulk mail goes to Newsletters, and what Spam Watch recognizes goes to Spam. Every rule here is one you can predict, because predictable beats clever.

Contacts

Your contacts are one file, MyContacts.vcf, on the Social desktop, in the vCard format that every phone and mail program can read. Open it and it's a table: name, categories, phone, email and organization, with a photo, a list of categories down the side, and a search box. You type over a cell to change it, the way you'd rename a file, and the book is written a minute after you stop. Anything more—a second phone number, an address, a birthday, a note—is on a contact's own sheet, whose photo takes a picture dropped on it. A book with nothing in it offers to bring in your Google contacts, and any vCard file dropped on the table is merged in.

A Contact Vouches

Mail from an address on one of your contact cards goes to the Inbox, unless Spam Watch finds a scam in it; a contact card doesn't excuse a message from being read. The match is the whole address, exactly, ignoring capitals: no guessing from names, and no matching on the part after the @. And a card doesn't vouch for mail that the server which received it says was forged. Nor does a card for your own address vouch for mail claiming to be from you. I learned that one the hard way, when six "YOU GOT RECORDED!" messages, from my own address to my own address, sat in my Inbox because my own card had waved them through. A contact card is not evidence of origin.

Strangers

Unknown Senders was my idea, and the reason for it is simple: if a new person writes, I want to see them, and add them to my contacts. A message from a stranger offers Add to Contacts..., which opens a card already filled in from the message; if there's already a card with that name, it asks whether to add the address to it or make a new one. A message from someone you already know offers Edit Contact... instead. Pick out several messages and Add Senders to Contacts... asks one question, listing who: "Their mail already here moves to the Inbox, and what comes later goes there."

The contact book is the authority, wherever it's changed: a couple of seconds after it changes, mail is sorted again, and anything in Unknown Senders that now has a voucher moves to the Inbox. Sort Mail does that on demand, and more: it looks through all the mail again—people you know to the Inbox, scams and spam to Spam, newsletters to Newsletters—and clears away out-of-date newsletters and old spam, saying what it's doing as it goes.

Spam

Mark as Spam... doesn't just move the message, because moving a single message solves nothing: the same sender writes again. It asks how to recognize messages like it from now on, by This sender, by Anyone at the sender's domain, by Anything from this mailing list when it came from one, or by This word or phrase in the subject, and says in a sentence what that will do. The rule then goes back through the mail already in the Inbox, Unknown Senders and Newsletters, sparing your contacts. Not Spam moves a message back to the Inbox and takes back the rule that caught it, which is the difference between a correction and a chore repeated every week; and no rule taught later will move that message back.

Spam Watch

Beyond your own rules, Spam Watch looks for what spam looks like:

• It believes only the verdicts of the server that actually received the message, not the claims a message makes about itself on the way.
• Mail that says it's from your own address, and isn't, is spam.
• The wording of extortion, together with a valid Bitcoin address, marks a scam.
• A domain registered in the last month or so counts against a message, though never decides on its own. Finding a domain's age means asking the public registry, once for each domain.
• Links are checked against a list of phishing sites from OpenPhish, downloaded once a day and checked here, so no link from your mail is ever sent anywhere to be looked up.

Newsletters

Bulk mail, the kind sent out to a mailing list, goes to its own basket, Newsletters, while receipts and other transactional mail stay where they'd otherwise go. Newsletters keep themselves tidy: from each sender, the older issues are replaced by the newest. The same tidying clears spam away after thirty days. Only mail the server has already let go of is cleared, though, or the next check would just collect it again; with Copy from host, nothing is cleared at all. And what is cleared goes to the Recycle Bin, never straight into oblivion, because a deletion that cannot be undone is not what clearing up a mailbox is for.

Not Yet

• Leaving a recognized scam uncollected on the server, rather than collecting it into Spam.
• More phishing lists than OpenPhish's.
• A way to teach the newsletter tidy by hand.
• Noticing when a contact's address changes, for the mail that was vouched for under the old one.