In each case, messages are converted from their native format to MIME when moving out of the PC LAN environment to PMDF, and from MIME to the native format when moving from PMDF into the PC LAN environment. Since some LAN mail systems do not have a way to indicate the type of data in a message part, provisions are made for mapping between PC filenames associated with attachments and MIME content-type labels. Using MIME as the interchange format insures that the form and content of messages generated by the various PC LAN messaging system can be full represented.

In addition to providing high performance message handling facilities for the LAN mail systems that PMDF-LAN serves, PMDF includes a set of directory coordination tools. The directory systems supported by these tools are listed below.

A general design rule of PMDF-LAN is to do as much of the actual message processing as possible on the PMDF host system and relying on support services of MS-DOS based applications only where it makes sense. In practice this means that for each LAN messaging system that PMDF supports, PMDF-LAN depends on software generated by the LAN mail system vendor to retrieve messages from the LAN message store, and to write messages into the LAN message store. These vendor supplied import/export utilities define a vendor specific file format that is understood by PMDF-LAN. These files are hereafter referred to as message drop files. The advantage to using this technique is that the messaging backbone implemented by PMDF is insulated from changes to the LAN messaging system.

Since messages destined for the LAN messaging systems are handled by PMDF-MTA first, PMDF-LAN is able to overcome some inherent limitations in PC-based SMTP gateways. Probably the most important limitation a PMDF-based solution overcomes is the poor performance of PC-based systems due to the single threaded nature of MS-DOS. PMDF-MTA will accept multiple messages destined for the LAN-based system asynchronously, and deliver them with PMDF-LAN synchronously.

It is possible to configure PMDF to insure that the binary attachments generated by the PC LAN message systems are correctly tagged with MIME content-types. This effectively deals with the problems associated with exchanging binary mail messages between different LAN user communities that have different standards for the definition of MS-DOS file names. The configuration can include the use of third-party format conversion utilities to perform document conversion as needed.

Once configured the delivery of messages to and from the PC LAN mail system is completely automatic.

Message Transport

PMDF-LAN requires that message drop files, files containing one or more messages, be available in both the PMDF and the PC LAN environments. There are several ways to accomplish this. All of the methods involve some processing in an MS-DOS environment. This processing environment is generally referred to as the support PC. The support pc function is frequently is performed on a dedicated PC, but it can be a DOS window on an OS/2 or Windows NT system as well. It should also be noted that a single support PC can be used to service more that one PC LAN postoffice.

Message Transfer Using File Service

Many commercial products are available that allow PC clients to access files directly on an OpenVMS or Unix system. In this environment the message drop files can be written onto disks that are that are directly accessible by PMDF processes. PMDF can use normal file access methods to read incoming messages and write outgoing messages.

Indirect Message Transfer

In numerous environments the PC file server and PMDF disk storage area are totally disjoint and it is not an option to use a Network Operating System like Netware as the method to make message drop files accessible to both the PMDF system and the PC postoffice server. How the files are transferred between the two environments is not critical. Thus, a wide variety of methods can be employed to move message drop files between the two environments. The three most common methods are described below.

1. The ability to move binary files between the support PC and the PMDF system.
2. A scripting facility to automate the connection, file transfer, and message delivery commands.

Most PC terminal emulation packages support the scripting facilities that are required to move message drop files to and from the PMDF system. While these transfers are quite straight forward it should be kept in mind that all file transfers need to be binary transfers.

Message Transfer Using NetWare Client

There is a special case where message drop files can be shared between the PC LAN environment and the PMDF system without installing a full Network Operating System file server on the PMDF system. This particular case allows an OpenVMS process to read and write files directly from and to a Novell NetWare file server's disks. It only applies when all four of the following conditions are met:

When this is your configuration, PMDF can use the MultiWare client API library to retrieve inbound messages directly from the NetWare server. PMDF also creates outbound messages directly on that same server's disks. All transfers are completely controlled and managed by processes on the OpenVMS system. In this configuration a support PC is still required to perform the import/export duties of moving of messages into and out of the LAN message store.

Software Requirements

Hardware Requirements

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