X.400 (source code)

= X.400
{wiki=X.400}

X.400 is a set of ITU-T (International Telecommunication Union Telecommunication Standardization Sector) standards that define a framework for electronic messaging and electronic mail. It was developed as part of the overall X.400 series of standards for office messaging and related applications. Key features of X.400 include: 1. **Message Structure**: X.400 specifies the structure of messages, including headers, body content, and attachments, supporting rich formatting and various data types.