The PMDF configuration file, presented in Section 1.2 above and described in more detail in Chapter 2, is the single most important PMDF file. Of only slightly lesser import is the alias file, described in Chapter 3. The existence of these two files is required. Listed below are some additional PMDF files and databases which are described elsewhere in this documentation:

File or database	Described in	Usage
Alias file and database	Chapter 3	Implements aliases, mail forwarding, and mailing lists.
Character set file	Chapter 29 and Chapter 30	Character set tables; used to translate between character sets.
Channel option files		Many channels use channel option files to set options particular to the channel. See the relevant channel documentation for details on what options, if any, are available for the channel.
Compiled configuration file	Section 8.1	Shareable image built with PMDF's cnbuild utility; contains information from the alias, configuration, mapping, conversions, security, system wide filter file, and PMDF option files; speed up PMDF's performance through the use of a compiled configuration.
Conversion file	Section 22.1	Used by the conversion channel to control message body part conversions; used to convert message attachments from one format to another.
Dispatcher configuration file	Section 11.3	Defines the PMDF server processes.
Domain database	Section 2.2.9	Domain rewriting rules stored in a database file; used primarily by BITNET configurations.
Forward database	Section 3.4	Address forwarding database, used primarily with autoregistered addresses.
General database	Section 2.2.6.5	Used for arbitrary, site-specific purposes.
IMAP server configuration file	Section 13.2.3.2.1	Sets options for the operation of the IMAP server
Job Controller configuration file	Section 10.1	On UNIX, defines the queues in which channels can run.
Log files	Section 2.3.4.84	There are two sorts of log files: those generated to record the run of a channel program ( e.g., a batch processing log file or channel debug log file), and the PMDF message and connection log file(s) such as mail.log, recording message flow through PMDF.
Mapping file	Chapter 5	Used by many different PMDF facilities as a repository of mapping tables; mapping tables are pattern based rules for transforming text-based data.
Message files	Section 1.5.1	Enqueued messages are stored in message files; message files are stored in channel queue directories.
Personal alias database	Section 3.1.3	User-level alias databases created with PMDF's db utility.
PMDF option file	Chapter 7	File of global PMDF options. Not to be confused with channel keywords specified in the configuration file or channel option files described in the channel documentation.
POP server configuration file	Section 13.2.3.2.2	Sets options for the operation of the POP server
Queue cache database	Chapter 29 and Chapter 30	The messages currently enqueued to PMDF and awaiting delivery are recorded in the queue cache database. Channel programs determine which messages to process by querying this database. PMDF's cache utility is used to manage this database.
Reverse database	Section 3.3.2	Database used to change addresses in outgoing mail messages; e.g., change alonso@naples.example.com into King.Alonso@Example.Com.
Security configuration file	Section 14.2	File controlling PMDF's authentication source and SASL use.

A schematic of these PMDF files and components and how they interact is shown in Figure 1-2 below.

Figure 1-2 The Structure of PMDF

The various components shown in Figure 1-2 are as follows.

1. The configuration file defines the specific channels and thus the transports that a particular PMDF installation can use. The configuration file also contains additional domain definitions like those in the domain database, except those in the configuration file are in plain text. This file must be present and be readable by all users of PMDF; if it is missing or unreadable PMDF will abort with an initialization failure.
2. The alias file is used to establish aliases and mailing lists, a special case of an alias. The alias file must be present and readable by all users of PMDF. The alias database performs functions similar to the alias file, except that it is an indexed file containing a list of mailbox names on the local system that are actually aliases for different addresses or collections of addresses. The presence and use of this database is optional.
3. The option file is used to set various PMDF parameters which are not specific to any one channel. In particular, the sizes of various tables internal to PMDF can be controlled using entries in this file.
4. The optional domain database is an indexed file containing information about the various domains a particular PMDF installation can reach. This database tells PMDF how addresses for the various domains should be formatted and what transport should be used to deliver messages to or obtain messages from a given domain.
5. PMDF uses a common set of routines, the MM routines, to enqueue messages in the channel queues.
6. The channel queues are used to store messages prior to a channel program's sending them out via a transport.
7. PMDF uses a common set of routines, the QU routines, to dequeue messages from the channel queues.
8. Channel programs are the parts of PMDF that interface to the various transports.
9. PMDF uses various transports to actually send and receive messages. Some of these are part of PMDF (e.g., PhoneNet) and some are not (e.g., DECnet, TCP/IP ).
10. The conversion routines implement the character set converters as well as the message encode/decode facilities used for handling encoded messages.
11. The mapping file is a repository for general mapping information used throughout PMDF. This file consists of a series of named tables written in a standard format. Various components of PMDF check for and use different tables for different purposes. For example, the SEND_ACCESS mapping table is used to control who can or can not send or receive mail from various channels.