As postal liberalization gains momentum, traditional postage meter markets are being transformed into digital meter markets for enterprise mailers. Modern technologies such as cryptography, digital signatures, hardware security devices, the Internet, 2D bar codes, and high-speed scanning equipment have come together to establish different flavors of electronic postage, addressing the needs of postal operators, private carriers and mailers. Electronic Postage Technology and Security introduces a taxonomy of electronic postage systems and explains their security risks and countermeasures. The underlying cryptographic mechanisms are introduced and explained, and the industrial-scale electronic postage systems existing worldwide are sorted out with respect to this taxonomy. The author also discusses privacy and anonymous mail, the state of standardization of electronic postage, and the process of security evaluation and testing of electronic postage systems.