> Has anyone proposed proof of work for email? Yes, the first was approximately contemporary with dinosaurs roaming the earth, before NCSA Mosaic was released

> Has anyone proposed proof of work for email? Yes, the first was approximately contemporary with dinosaurs roaming the earth, before NCSA Mosaic was released and images appeared in webpages also known as the year 1992. > We present a computational technique for combatting junk mail in particular and controlling access to a shared resource in general. The main idea is to require a user to compute a moderately hard, but not intractable, function in order to gain access to the resource, thus preventing frivolous use. https://link.springer.com/content/pdf/10.1007%2F3-540-48071-4_10.pdf https://link.springer.com/content/pdf/10.1007%2F3-540-48071-... Dwork C., Naor M. (1993) Pricing via Processing or Combatting Junk Mail. In: Brickell E.F. (eds) Advances in Cryptology — CRYPTO’ 92. CRYPTO 1992. Lecture Notes in Computer Science, vol 740. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-48071-4_10 https://doi.org/10.1007/3-540-48071-4_10