Lee Stein (et al) holds 3 United States Patents for Computerized Systems that govern financial transactions over the Internet via e-mail.

Patent 1 - 5,757,917 - Computerized Payment System for Purchasing Goods and Services on the Internet.

Patent 2 - 5,826,241 - Computerized System for Making Payments and Authenticating Transactions over the Internet.

Patent 3 - 6,246,996 - Computerized System for Facilitating Transactions between Parties on the Internet Using E-Mail.