UTF-7 was first proposed as an experimental protocol in RFC 1642, "A Mail-Safe Transformation Format of Unicode". This RFC has been made obsolete by RFC 2152, an informational RFC which never became a standard. As RFC 2152 clearly states, the RFC "does not specify an Internet standard of any kind". Despite this, RFC 2152 is quoted as the definition of UTF-7 in the IANA's list of charsets. Neither is UTF-7 a Unicode Standard. "The Unicode Standard 5.0" only lists UTF-8, UTF-16 and UTF-32.