X400: Definition of X.121 Address

The information in this article applies to:

• Microsoft Mail Gateway to X.400, version 3.0

The X.121 is an address that enables packets to be sent to people on a public data network. The X.25 network uses X.121 addresses to determine routing within the X.25 network.

The X.121 address can be equated to a voice phone number on a telephone network.

The X.121 address length for an international data number is a 10-digit numeric character set from 0 to 9. The number formats for various data accesses are as follows:

   International data number:

      P + DNIC + NTN

   Or, if the number is part of a national integrated numbering scheme:

      P + DCC + National Number

   Public telephone network:

      P + 9 + TCC + National Significant Telephone Number

   Public Telex network

      P + 8 + TDC + National Telex Number

   Acronym   Description
   -------   -----------

   DCC       Data country code (3 digits)
   DNIC      Data network identification code (4 digits)
   NTN       Network terminal number)
   P         International prefix
   TCC       Telephone country code
   TDC       Telex destination code