Felix Salmon writes this morining in exasperation:

Let Me Pay to Send Email!

...

What I'd love is some mechanism whereby I could pay "postage" of a few cents, maybe to charity, on selected emails I send. That would be a very strong indication my message was not spam, and should be let through. But I fear coming up with a universal standard for such a mechanism is practically impossible.

A few years ago, a good friend and I were toying with the idea of a tech start-up. (This was post-crash, but we're both really unreconstructed new economy types.) I offered a proposal that I thought had a very short shelf life. Someone surely would do something like this, soon. Hah!

We would start an e-mail service that would require mail to be "stamped". You could sign up for it like any e-mail service, but if anyone sent mail to your address and it didn't have a stamp, it would bounce with an explanation of how to supply postage. No new standards or internet infrastructure would be required.

The receiver of the mail would set the postage rate and get the money. That is, you do not pay a postal service for delivering mail (that's free in the internet age), you pay the recipient for the burden your correspondence places upon her attention. When mail is delivered, it would include a convenient link whereby you could refund the postage to the sender with a single click. Among frequent correspondents, the postage would be refunded as a matter of course. It would serve as a guarantee of nonabusiveness, but would rarely be paid. Therefore, people could set their postage rates fairly high without losing mail they care about. (One could set-up whitelists of senders whose postage would reimburse automatically, and blacklists of senders whose mail and postage are both refused. Importantly, postage need not vouch for the identity of a sender, but need only associate a letter with an account from which postage has been properly drawn.)

Mail from strangers would not ordinarily be reimbursed, and would serve as a potential source of revenue for people whose attention is in great demand. Although senders would have no guarantee that mail with postage would actually be read, recipients would be encouraged to set a rate at which they'd be willing to give a quick read to a one or two page letter. Famous people could give out real e-mail addresses freely, and use the price mechanism to control the quantity of mail they actually have to sort through. Ordinary blokes would have a means to reach the powerful and famous, at a price. (Of course, senders might often plead poverty and beg that the postage be reimbursed. But mailing would be at senders' risk. If a recipient is unimpressed with a letter, by default they pocket the cash.)

Also, various kinds of businesses might sprout up using incoming mail as a payments mechanism. These might range from informal consulting gigs (experts on various topics who generally respond to paid questions, that'd be very nice for open-source software support for example) to the email equivalent of 1-900-SEX-LINEs. Whatever. Let a thousand flowers bloom.

A scheme like this could be implemented incrementally, without changing any internet standards. Mail service providers would offer POP, IMAP, or web e-mail access, but would require that incoming mail to have an encrypted header or attachment indicating an account from which postage could be drawn (up to some amount, for a limited period of time, for a specific letter). If the token is present and payment succeeds, the mail is delivered to the user. If not, it is bounced. Mail service providers would earn revenue by taking a fraction of unreimbursed postage payments. Because a monopoly mail service provider is implausible and undesirable, the business model here would be to build software and a payments infrastructure, à la MasterCard, something aspirant competitors would prefer to use than to reconstruct. The goal would be postage interoperability. On the software side, the hardest part would be making postage-payment convenient. One could start decently but imperfectly (e.g. how e-mail-to-fax services bill), but hope to get embedded in popular e-mail clients. Initially, one would market the service as a free, secondary, spam-free e-mail account, and try to get some prominent people to offer publish addresses and postage rates. No one need abandon their traditional, free e-mail accounts, but if managing spam is as costly to others as it is to me, there'd be plenty of incentive to encourage correspondents to migrate in order to reduce the need to monitor open spools.

Legitimate commercial correspondents and opt-in mailing lists would expect to have postage reimbursed, but could not enforce that via the mail system. They would have to establish a contractual relationship prior to mailing, stating that unreimbursed postage payments from certain addresses could be billed back to the recipient. That's a feature, not a bug. Attention is too scarce a resource to commit as lightly as with a webform checkbox set by default.

Ideas like this have been bouncing around the internet for a long time. I don't pretend this is particularly novel. I don't know that it could work. It astonishes me, though, that, as far as I can tell, no one has ever made a serious attempt to do this kind of thing.

Update: In the comments, Richard Serlin points to a very nice, similar proposal by Marshall Van Alstyne. (I know there are more out there, somewhere in the archives of Slashdot.) In Alstyne's proposal the recipient opts to take, rather than opting to reimburse, which might be a better "choice architecture". That way you don't piss your friends off just by having forgetten to click a link.