Incoming X.400 network connections from remote X.400 MTAs must be associated with the PMDF-X400 responder.
On Digital UNIX, if you are using OSI transport, you must define a PMDF-X400 service, see Section 41.6.1 , and then you must start up the PMDF-X400 TSAPD process. If you are using TCP/IP transport, you simply start up the PMDF-X400 TSAPD process. The PMDF-X400 TSAPD process listens for incoming X.400 network connections and hands them to PMDF-X400; see Section 41.6.2 for a discussion of starting up this process.