A method and apparatus for enabling message transmission between multiple communication environments such as the Internet and a wireless communications network, wherein user authentication and billing may be performed and wherein access rights associated with one environment may be advantageously inherited by another. The method enables the transmission of electronic messages (such as e-mail or SMS text messages) by registering two or more individual identities, each represented by a communications handle (such as an e-mail address or a mobile phone number), and by associating each of these two or more registered identities with each other, binding them into an equivalence class of identities, wherein one or more attributes of at least one of these identities becomes associated with the other identity. Illustratively, a sender-pays business (i.e., billing) model for e-mail to mobile message transmission and access rights to an internal enterprise database from a mobile phone are advantageously enabled.