This Recommendation | International Standard specifies the means by which messages are routed through the MHS, and

supplements the procedures defined in 14.3 of ITU-T Rec. X.411 | ISO/IEC 10021-4.

Other Recommendations | parts of ISO/IEC 10021 define other aspects of the MHS. ITU-T Rec. F.400/X.400 | ISO/IEC

10021-1 defines the user-oriented services provided by the MHS. ITU-T Rec. X.402 | ISO/IEC 10021-2 provides an

architectural overview of the MHS. ITU-T Rec. X.411 | ISO/IEC 10021-4 defines the abstract-service of the Message

Transfer System.