# Scope USEF defines the content of XML messages between role processes, as required for implementation of USEF’s MCM. Each message has a unique recipient, identified by the Internet domain and USEF role of the participant. The message transfer mechanism is responsible for sending and receiving these messages.

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When selecting a message transfer mechanism, local market conditions should be considered and the USEF privacy and security guidelines should be followed [^B5]. Further recommendations about the message transport mechanism are given in [Message transport mechanism](../appendix/message-transport-mechanism.md). [^B5]: USEF Foundation, "USEF: The Privacy and Security Guideline," USEF Foundation, Arnhem, 2015. Available: [https://www.usef.energy/app/uploads/2016/12/USEF_PrivacySecurityGuideline_3nov15.pdf](https://www.usef.energy/app/uploads/2016/12/USEF_PrivacySecurityGuideline_3nov15.pdf)