How do you filter spam?

Take a clue from Yahoo. When you try to set up an email account there, Yahoo requires that you copy a small word from a graphic that appears on the page, and type the word into a form. This way, no machine can read the word and create an account - it requires a human to create every account.

How about a similar feature for your email? Whenever you send out an email, it somehow includes a graphic with a unique word in it. In order to reply to the email, the person has to read the word from the graphic and type it - perhaps into the subject line of the email or whatever - and if the email does not have this string in it, your email reader filters it out.

Not hard to do. You can have a key in your email reader. This key can be satisfied by a very large number of possible word entries. Each time you send out an email, a mechanism generates a graphical word that will satisfy the key, and puts the graphic into the email. The person you email is required to see the graphical word and enter it into the subject line of the reply. And, each time you receive an email, the mechanism checks the "subject" line for any string that will satisfy the key.

Similar, non-graphical method

Simply require everyone who emails you (or replies) to place a certain key phrase in the subject line.

Another mechanism

This would require changes in the way mail servers work. When you send someone an email, it creates some set of words in the header file, and these same words are returned in the header file of any reply email. Your mail system filters to only accept incoming email with those words in the header. Therefore, anyone who merely possesses your email address cannot email you. You are only able to accept replies.

Problems

One problem with all these methods is that they eliminate incoming email from machine-driven services that you might want - like listservers etc. But you could "white-list" those. It also eliminates email from old friends, etc. What it means is that only humans who have a dynamic connection with you and who keep in contact would be able to email you. You could accomplish just about as much by changing your email address every few weeks.

Rob Weinberg, 3/15/03