Soft*Switch X.400 Gateway: This product connects with Soft-Switch Central on IBM mainframes (MVS or VM) and provides a gateway to X.400(84) P1/P2 for typically large organizations who connect themselves as a PRMD to public service/ADMDs. Any e-mail system or application that connects to Soft-Switch Central, via standards-based or proprietary protocol can exchange e-mail across the X.400 Gateway (typically, there are many). The product is in production use by many large commercial organizations in the US and Europe.
EMX, The Enterprise Mail Exchange: EMX is a family of manageable X.400 enterprise mail backbone switches that includes directory services and interoperability with e-mail systems utilizing existing protocols such as SMTP, IBM's SNADS, MHS, and others protocols. The core of EMX is a 1988 X.400 MTA providing MTA-to-MTA P1/P2 support, which can be configured to also support 1984 P1/P2 for interoperability with most of today's X.400 implementations.
This information supplied by Dena Bauckman <dtb@ssw.com>