Provided by: libmail-box-perl_3.004-1_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 where 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 3.004, built on December 22, 2017.
Do not forget to read Mail::Box-Overview, Mail::Box-Cookbook, and Mail::Box-Index.
Examples are included in the Mail-Box distribution, directories 'examples' and 'scripts'.
Browseable manuals, papers, and other released material van be found at Website:
http://perl.overmeer.net/mailbox/
The central modules (in separate distributions) in the MailBox suite are: Mail::Message,
Mail::Box, Mail::Box::IMAP4, Mail::Box::POP3, Mail::Box::Parser::C, Mail::Box::Dbx
(unpublished), Mail::Transport, Object::Realize::Later, and User::Identity.
Please post questions or ideas to the author markov@cpan.org.
LICENSE
Copyrights 2001-2017 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/