Provided by: libmail-box-perl_3.010-2_all 
NAME
Mail::Box-Overview - objects used by Mail::Box
DESCRIPTION
Introduction
The MailBox package is a suite of classes for accessing and managing email folders in a folder-
independent manner. This package is an alternative to the "Mail::Folder" and "MIME::*" packages. It
abstracts the details of messages, message storage, and message threads, while providing better
performance than older mail packages. It is meant to provide an object-oriented toolset for all kinds of
e-mail applications, under which Mail User-Agents (MUA) and mail filtering programs.
This package is modular --parts of it can be used independently of the rest. For example, the
Mail::Box::Manager can automatically determine that a folder is in Mbox format and return an object of
the Mail::Box::Mbox class, or the user program can bypass the manager and create Mail::Box::Mbox objects
directly. Similarly, if the user program is only manipulating a single message, a Mail::Message.
The Mail::Box package has special features to help MUA's access folder data quickly in random order. You
will not really benefit (neither slower) if you need the full folder sequentially.
You may want to have a look at the sample scripts in the "scripts" directory.
Distributions
Up to MailBox v2, all "Mail::*" modules were released as a single distribution. From v3, there are a few
separate distributions in an attempt to reduce the dependencies:
• Mail::Message
• Mail::Transfer
• Mail::Box
• Mail::Box::IMAP4
• Mail::Box::POP3
• Mail::Box::Parser::C
The names of the classes are not always ideal: the 'Mail' namespace on CPAN is quite full.
The class relations
Mail::Box::Manager objects play a central role in any program which is built with MailBox. Each program
will create one manager, and then open folders via that manager. Besides folders, the manager can also
be used to discover message threads: sequences of messages with their follow-ups.
<has-a> Mail::Box::Mbox
Mail::Box::Manager <---------* (Mail::Box::MH)
^ : (Mail::Box::Maildir)
| (maintains) (Mail::Box::POP3)
| :
| :
`---------------------* Mail::Box::Thread::Manager
(<has-a>)
Each folder maintains a list of messages. Much effort is made to hide differences between folder types
and kinds of messages. Your program can be used for MBOX, MH, Maildir, and POP3 folders with no change
at all (as long as you stick to the rules).
Mail::Box::Mbox <-----------* Mail::Box::Mbox::Message
^ <has-a> ^
| <isa> | <isa>
| |
Mail::Box ............. Mail::Box::Message
^
| <isa>
|
Mail::Message
/ \
<has-a>
/ \
Mail::Message Mail::Message
::Body ::Head
The situation for MH and Maildir folders is a little more complicated, because they have an extra
intermediate level of abstraction: Mail::Box::Dir. The POP3 folder has an intermediate Mail::Box::Net.
In the future, when more Mbox-like folder types get implemented, there may be a Mail::Box::File level
too. The following is also true for the mail boxes
MB::MH::Message MB::POP3::Message
\ MB::Maildir::Message /
\ / /
\ / MB::Mbox::Message /
\ / | /
MB::Dir::Message | MB::Net::Message
\ | /
\ | /
MB::Message
|
|
Mail::Message
The Manager
The mailbox manager Mail::Box::Manager encapsulates folder management issues. It maintains a set of open
mail folders (mailboxes), and provides methods for opening and closing them, efficiently moving messages
between folders, and efficiently appending messages to folders. It contains Mail::Box objects which may
be of different types. Most folder types can be detected automatically.
The main manager also manages message-thread detector objects, and informs them when the contents of a
folder have changed. This manager class is the only one you instantiate yourself: objects of all other
classes will be provided by your folder manager.
You are strongly advised to use this object, but you can often do without it and open a specific folder-
type directly.
The Messages
Mail::Message
A base class that defines an interface for manipulating the head and body of a message. There are
various header object types (Mail::Message::Head's) and a bunch of body object types
(Mail::Message::Body's).
The Mail::Message::Construct package is loaded when more complex tasks have to be performed on
messages, like creating replies, bounces, or a forward message. These functionalities are described
and implemented in the ::Construct file, but are automatically added to the Mail::Message namespace
when used.
Message types which are foreign to MailBox can be used in the MailBox environment: there are some
converters implemented via Mail::Message::Convert. Particularly the popular Mail::Internet and
MIME::Entity are supported.
Mail::Box::Message
An abstract base class which defines an interface for mail messages which are stored in any folder.
It inherits from Mail::Message, and adds the basic idea of location to a message.
Mail::Message::Body
This is the base class for all message bodies. It describes what you can do with any kind of body.
The body types differ on the way how the keep the body content during the run of your program.
One special case of the body types is the Mail::Message::Body::Multipart, which contains a set of
Mail::Message::Part objects. These are just like normal messages, except that they are contained in
an other message. The Mail::Message::Body::Nested body type is comparible, but contains only one
message: they are used for "message/rfc822" message encodings.
When needed, the functionality of the body objects is extended with Mail::Message::Body::Construct
and Mail::Message::Body::Encode. The former package implements things like concatenation, the later
controls message encoding and decoding. In the current implementation this is limited to transfer
encodings (implemented in the Mail::Message::TransferEnc packages). Automatic character and mime
recodings are on the wish-list.
Mail::Message::Head
The header for a single message. Maintains a set of Mail::Message::Field objects, each containing one
header line. Fields are the only objects which have no logging and tracing facilities, purely for
reasons of performance.
The header object has three sub-classes: the Mail::Message::Head::Complete version knows all lines
for sure, Mail::Message::Head::Subset maintains an unknown subset of lines, and the
Mail::Message::Head::Delayed has no lines yet but knows where to get them.
The latter two will automatically get the missing header lines from the mailbox files when needed,
and so transform into a "::Complete" header. It is fully transparent to the user of MailBox in which
shape the header really is on the moment.
The Folder types
Mail::Box
A base class that defines a standard interface for mail boxes which is independent of mailbox type.
Objects of this class contain a Mail::Box::Locker and a list of Mail::Box::Message objects.
Mail::Box::Dir
The base class for all folders which use a directory organization: each message is a separate entity
(file) grouped in a directory. Each Mail::Box::Dir::Message represents one message, one such entity.
Mail::Box::Net
The base class for all folders which have the messages outside direct reach of the MailBox library,
for instance on a remote system, or in a database.
Mail::Box::Mbox
This class derives from Mail::Box, and implements its interface for mbox-style folders. It maintains
a set of Mail::Box::Mbox::Message objects, which are derived from a Mail::Box::Message.
Mbox-style folders have one file containing multiple messages per folder. When folders get large,
access tends to get slow.
Mail::Box::MH
This class derives from Mail::Box::Dir, and implements its interface for MH-style folders. It
maintains a set of Mail::Box::MH::Message objects, which are derived from a Mail::Box::Dir::Message.
MH-style folders are represented by a directory, where each message is stored in a separate file.
The message files are sequentially numbered. It is fast to open one single message, but hard to get
an overview.
Mail::Box::MH::Index
The base class for MH mailbox indexes which provides methods for reading, writing, and managing
message indexes. These indexes are used to speed-up access to directory based folders.
Mail::Box::MH::Labels
Also for efficiency reasons, a separate file is maintained which contains flags about the messages.
This file for instance lists new files. This way, the MH message files do not have to be opened to
find that out.
Mail::Box::Maildir
Like the MH folder type, this class derives from Mail::Box::Dir. It implements its interface for
Maildir-style folders. It maintains a set of Mail::Box::Maildir::Message objects, which are derived
from a Mail::Box::Dir::Message.
Mail::Box::POP3
Implements the POP3 protocol based on Mail::Box::Net. The Mail::Transport::POP3 implementation
handles the protocol details. In this kind of folders, you can only read and delete messages.
Various Other Classes
Mail::Box::Thread::Manager
Maintains a set of message-threads over one or more folders. A message-thread is a start message
with all the replies on it. And the replies on replies, and so on. This object is used to construct
the thread for a set of open folders.
This object maintains linked lists of Mail::Box::Thread::Node objects. Mail::Message::Dummy's fill-
up some holes.
Mail::Box::Locker
Provides a folder locking interface which is inherited by the Mail::Box class. Currently it supports
dot-file locking ("filename.lock"), flock filehandle locking, and locking over NFS. Each is
implemented in a separate class. A multi-locker, using a set of lock-methods at the same time is
also available.
Mail::Box::Search
The set of search packages implement various search techniques in an uniformal way. Although
implementing your own search algorithm is simple in general, in practice multiparts, encodings, and
mime-types complicate things.
Mail::Box::Parser
The parser reads messages, and transforms them into data-structures such that the content of header
and body can be used within the program. The first parser is implemented in pure Perl. A second
parser is under development, and will written in C, to gain speed.
Mail::Box::Tie
Provides hash (Mail::Box::Tie::HASH) or array tied (Mail::Box::Tie::ARRAY) access to any mail folder
derived from Mail::Box. This beautifies your code in some applications.
Mail::Transport
Various ways of sending and receiving messages are implemented. Sending is possible via external
programs, like "mail", "Mailx", "sendmail", or autonomously with direct SMTP. Receiving is currently
only implemented via POP3.
Mail::Reporter
A debugging and logging class which is inherited by most of the Mail:: modules. For each object, you
can say what log and error reports must be kept or directly presented to the user. This way you can
decide to have Mail::Box report about problems, or do it all yourself.
All classes are written to be extensible.
SEE ALSO
This module is part of Mail-Box distribution version 3.010, built on July 18, 2023. Website:
http://perl.overmeer.net/CPAN/
LICENSE
Copyrights 2001-2023 by [Mark Overmeer]. For other contributors see ChangeLog.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl
itself. See http://dev.perl.org/licenses/
perl v5.36.0 2023-12-11 Mail::Box-Overview(3pm)