@MASTERSTHESIS\{IMM2005-03854,
    author       = "L. L. Jensen, and J. Irsberg",
    title        = "Fighting spam",
    year         = "2005",
    school       = "Informatics and Mathematical Modelling, Technical University of Denmark, {DTU}",
    address      = "Richard Petersens Plads, Building 321, {DK-}2800 Kgs. Lyngby",
    type         = "",
    note         = "Supervised by associate professor Christian Damsgaard Jensen",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/3854-full.html",
    abstract     = "(Project language: Danish)

Up until now spam email has become more and more of a problem for almost all users of the global internet mail system. It costs valuable time and resources to deal with and clogs up our inboxes increasingly. 

Most solutions seen today try to deal with the problem through filtering and blacklisting. All but a few of them with limited success since spammers exploit holes in the filtering schemes and the email system itself is inherently insecure, making effective blacklisting of spammers impossible. 

In this project we aim to stop spamming by removing the financial incentive for sending spam all together. The solution is based on the existing mail system and works by financially penalizing those who send spam while rewarding those who receive it. Briefly explained this is achieved by requiring a small payment sent along with each email. This payment is returned to the sender if the receiver does not categorize the email as spam. This means that ideally only spammers will pay for using the mail system while for those of us who use it as intended; it will remain cost-free."
}