Each site must provide a mechanism to transfer message files in both directions. The solution chosen is very site specific. The number of permutations make it impossible to determine the best approach a priori. Factors include PC mail system setup, the type of PC LAN, the PC network operating system, file server configuration, geographic distribution, and administrative style and policies.

All the transfers must be done in binary mode. If the files are moved using a non-binary mode, corruption of the PC specified file formats can result. Such corruption can be difficult to detect, particularly in attachments (spreadsheets, executable programs, etc.).

Various utilities to assist in moving messages are provided as part of PMDF. Other programs can be appropriate. These programs usually need to execute on a transfer PC which can simultaneously access the file server hosting the PC mail system as well as the PMDF disk storage system.

Describing all of the possible variations in transferring files between a PC and PMDF system is beyond the scope of this manual: it depends on the products currently available in the market as well as the specific network topology in used. Several workable scenarios are covered below. It is not a complete list of the products available nor is it meant to be. It just attempts to give some hints as to the possible solutions that can satisfy this requirement.

To aid in automating transfers between PMDF and PC mail systems, immediately before each PMDF-LAN channel runs, PMDF will look for and execute, if it exists, a site-supplied PMDF_COM:pc_prepare.com procedure (OpenVMS) or /pmdf/bin/pc_prepare shell script (UNIX). Immediately after each PMDF-LAN channel runs in master mode but before it runs in slave mode, PMDF will look for and execute, if it exists, a site-supplied pc_transfer.com procedure (OpenVMS) or pc_transfer shell script (UNIX). Finally, pc_cleanup.com (OpenVMS) or pc_cleanup (UNIX) is executed, if it exists, after the channel finishes running. Such site-supplied command procedures or shell scripts can effect or initiate a transfer of the message files to the PC mail system. The procedure can determine the name of the PMDF channel being processed (e.g., cc_local, mhs_local, cc_newyork, etc.) from the PMDF_CHANNEL logical (OpenVMS) or PMDF_CHANNEL environment variable (UNIX).
On OpenVMS, note that the command procedure should only define local symbols and user mode or process logicals. Moreover, as this procedure can be executed from a detached process of the PMDF Process Symbiont, it should not make lasting changes to the process's environment or exit the running process.

Several example transfer mechanisms are described in the next sections.