M-Switch X.400 is a high-performance, versatile Message Transfer Agent (MTA) which can be deployed either to support local users or as a gateway, switching messages between other MTAs. M-Switch X.400 is widely used in Civil Aviation, EDI and Military environments.


M-Switch X.400 is sold in two configurations:

  1. M-Switch X.400: Gateway/Backbone. Can be used to switch messages between other MTAs and/or converting between X.400 and another protocol (excluding X.400/SMTP conversion which is covered by M-Switch MIXER.
  2. M-Switch X.400. An MTA used to support local X.400 users either directly through P3 or indirectly through M-Store X.400 with P7. Local MTA use excludes P1 to P1 switching and use as a gateway.

Both configurations include ACP142 for use with Data Diodes and STANAG 4406 for military messaging, but not for deployment on constrained bandwidth networks (see M-Switch Constrained Network Server/Gateway for ACP142 and STANAG 4406 Annex E for constrained networks). In addition to core features, discussed on this page, the following add-ons are available for this product:

  • M-Switch Encyption: Enabling message encryption and decryption capabilities (using STANAG 4406 Encryption for X.400 messages)
  • M-Switch ACP127: Enabling message conversion to/from ACP127 and related protocols.

Deployment Targets

M-Switch X.400 can be deployed in the following ways:

  • As a "Backbone MTA", whose role is primarily to connect together other X.400 MTAs, acting as a P1 switch, providing high performance switching and robust message routing.
  • As a "Local MTA" (or "Departmental MTA") used to provide X.400 support to end users by use of User Agents. In this situation, M-Switch X.400 will often be used in conjunction with M-Store X.400 to provide mailbox storage for X.400 P7 User Agents.
  • As a "Border MTA", to provide connection between different X.400 domains using capabilities such as authorization, security label handling and anti-virus.

M-Switch X.400 is widely used in Military, Civil Aviation and EDI solutions, further details can be found on the pages for those markets.

Key Benefits

Notable strengths of M-Switch X.400 are described below. Reasons why this product may be of particular interest include:

Full X.400 Support

M-Switch is conformant to the most recent X.400 standards (X.400 (1999)) offering very high functionality, and offering X.400 P3 support as well as X.400 P1.

Excellent scheduling and operational characteristics

The Queue Manager (QMGR) and channel architecture described below enables a sophisticated scheduling approach, which combined with the Message Switch's queue structure leads to a product which works exceedingly well in demanding operational environments. For more details see the M-Switch Queue Manager page.


M-Switch products use Transport Layer Security (TLS) for data confidentiality and Simple Authentication and Security Layer (SASL) for authentication. SASL is also used to map simple identifiers onto directory names for authentication. A wide range of SASL authentication mechanisms are supported.

M-Switch products can check S/MIME signatures on message submission, to validate message integrity and origination. These checks are integrated with the authorization system, so messages can be controlled based on signature presence and validity. S/MIME Encryption is supported by M-Switch Encryption, which is a capability that may be added to all M-Switch products. You can read more about the security features common to all M-Switch products.

High Availability

M-Switch X.400 has exceptional robustness and stability, including support for fail-over clustering and off-site hot standby.

Military Email using STANAG 4406

STANAG 4406 is the NATO standard for Military Messaging based on X.400. STANAG 4406 defines a number of functional and security features to support formal military messaging. It is particularly important for High Grade Messaging, where features of X.400 to support high reliability are used.

This page on Military Email using STANAG 4406 describes the STANAG 4406 (and ACP 123, which is technically aligned) features in M-Switch X.400 and M-Switch MIXER. A separate page provides a broader overview of Isode products for Military Messaging.

The M-Switch Message Profiler operates directly on STANAG 4406 messages as well as RFC 6477 messages (a capability of M-Switch SMTP) and ACP127 (available as an add-on to both M-Switch SMTP and M-Switch X.400 products).


M-Switch X.400 uses directory based configuration, with configuration and user agent information stored in Isode's M-Vault directory. MConsole, Isode's management GUI for messaging, connects to the directory using an Isode Bind Profile, shared with Isode GUIs that access the directory. Multiple messaging configurations can be managed from MConsole.

MConsole also provides detailed operational monitoring of multiple M-Switch instances, providing operator functions which are a critical part of a managed messaging service including message tracking and queue monitoring. More information on X.400 Configuration Management and Operational Management can be found by following the links.