The problem of spam is a classic “tragedy of the commons” [10]. We propose the Zmail protocol as a way to preserve email as a “free” common resource for most users, while imposing enough cost on bulk mailers so that market forces will control the volume of spam. A key idea behind Zmail is that the most important resource consumed by email is not the transmission process but the end user’s attention. Zmail requires the sender of an email to pay a small amount (called an “e-penny”) which is paid directly to the receiver of the email. Zmail is thus a “zero-sum” email protocol. Users who receive as much email as they send, on average, will neither pay nor profit from email, once they have set up initial balances with their ESPs (Email Service Providers) to buffer the fluctuations. Spammers will incur costs that will moderate their behavior. Importantly, Zmail requires no definition of what is and is not spam, so spammers’ efforts to evade such definitions become ir...
Benjamin Kuipers, Alex X. Liu, Aashin Gautam, Moha