meillo@39: .RN 1
meillo@197: .H0 "Introduction
meillo@197: .Id introduction
meillo@39: 
meillo@0: .P
meillo@227: MH is a set of mail handling tools with a common concept.
meillo@227: It is similar to the Unix tool chest, which is a set of file
meillo@227: handling tools with a common concept.
meillo@227: \fInmh\fP is the currently most popular implementation of an
meillo@53: MH-like mail handling system.
meillo@53: This thesis describes an experimental version of nmh, named \fImmh\fP.
meillo@53: .P
meillo@32: This chapter introduces MH, its history, concepts and how it is used.
meillo@47: It describes nmh's code base and community to give the reader
meillo@227: a better understanding of the project's condition at the time when
meillo@227: mmh started off.
meillo@181: Furthermore, this chapter outlines the mmh project itself,
meillo@47: describing the motivation for it and its goals.
meillo@8: 
meillo@0: 
meillo@28: .H1 "MH \(en the Mail Handler
meillo@197: .Id mh
meillo@0: .P
meillo@47: MH is a conceptual email system design and its concrete implementation.
meillo@212: MH had started as a design proposal at RAND Corporation,
meillo@47: where the first implementation followed later.
meillo@47: In spirit, MH is similar to Unix, which
meillo@42: influenced the world more in being a set of system design concepts
meillo@32: than in being a specific software product.
meillo@47: The ideas behind Unix are summarized in the \fIUnix philosophy\fP.
meillo@207: .[
meillo@207: gancarz unix philosophy
meillo@207: .]
meillo@42: MH follows this philosophy.
meillo@2: 
meillo@11: .U2 "History
meillo@2: .P
meillo@32: In 1977 at RAND Corporation, Norman Shapiro and Stockton Gaines
meillo@209: proposed the design of a new mail handling system,
meillo@207: .[
meillo@207: shapiro gaines mh proposal
meillo@207: .]
meillo@209: to superseed RAND's old monolithic \fIMail System\fP (MS).
meillo@212: One year later, in 1978, Bruce Borden picked up on the
meillo@209: proposal and implemented a prototype, which he called
meillo@209: \fIMail Handler\fP (MH).
meillo@106: Before the prototype's existence, the concept was
meillo@47: believed to be practically unusable.
meillo@209: But the prototype \(en written in only three weeks \(en
meillo@212: proved successful and replaced MS thereafter.\&
meillo@209: .[ [
meillo@209: rand note design of mh
meillo@209: .], p. 4]
meillo@2: .P
meillo@106: In the early eighties,
meillo@106: the University of California at Irvine (UCI) started to use MH.
meillo@106: Marshall T. Rose and John L. Romine then became the driving force.
meillo@57: They took over the development and pushed MH forward.
meillo@209: .[ [
meillo@209: rand note design of mh
meillo@209: .], p. 4]
meillo@57: RAND had put the code into the public domain by then.
meillo@212: MH was developed at UCI at the same time when the Internet appeared,
meillo@212: BSD started to support TCP/IP networking,
meillo@209: and Eric Allman wrote Sendmail.
meillo@47: MH was extended as emailing became more featured.
meillo@209: The development of MH was closely related to the development of email RFCs.
meillo@204: In the advent of the \fIMultipurpose Internet Mail Extensions\fP (MIME),
meillo@204: MH was one of the first implementations of the new email standard.
meillo@2: .P
meillo@117: In the nineties, the Internet became popular and in December 1996,
meillo@181: Richard Coleman initiated the \fINew Mail Handler\fP (nmh) project.
meillo@212: Nmh is a fork of MH 6.8.3 and bases heavily on the
meillo@47: \fILBL changes\fP by Van Jacobson, Mike Karels and Craig Leres.
meillo@207: .[
meillo@207: lbl changes
meillo@207: .]
meillo@32: Colman intended to modernize MH and improve its portability and
meillo@32: MIME handling capabilities.
meillo@47: The development of MH at UCI stopped after the 6.8.4 release in
meillo@47: February 1996, soon after the development of nmh had started.
meillo@212: Today, nmh is developed openly in the Internet community.
meillo@212: It has almost completely replaced the original MH.
meillo@212: Some systems might still provide the old MH, but hardly for good reasons.
meillo@47: .P
meillo@212: In the last years, the majority of changes in nmh was maintenance work.
meillo@212: Nevertheless, the development was revived in December 2011
meillo@57: and stayed busy since then.
meillo@0: 
meillo@197: 
meillo@11: .U2 "Concepts
meillo@0: .P
meillo@53: MH consists of a set of tools, each covering a specific task of
meillo@209: email handling, such as composing a message, replying to a message,
meillo@53: refiling a message to a different folder, listing the messages in a folder.
meillo@209: The tools are invoked directly from the Unix shell.
meillo@209: .[
meillo@209: a rand note design of mh
meillo@209: .]
meillo@42: .P
meillo@209: The tools operate on a common mail storage, which consists of
meillo@209: \fImail folders\fP (directories) and \fPmessages\fP (regular files).
meillo@209: Each message is stored in a separate file.
meillo@209: .[
meillo@209: a rand note design of mh
meillo@209: .]
meillo@47: The files are named with ascending numbers in each folder.
meillo@47: The specific format of the mail storage characterizes MH in the same way
meillo@106: as the format of the file system characterizes Unix.
meillo@42: .P
meillo@164: MH tools maintain a \fIcontext\fP, which includes for instance the
meillo@164: current mail folder.
meillo@32: Processes in Unix have a similar context, containing the current working
meillo@32: directory, for instance. In contrast, the process context is maintained
meillo@32: by the Unix kernel automatically, whereas MH tools need to maintain the MH
meillo@32: context themselves.
meillo@106: The user can have one MH context or multiple ones; he can even share it
meillo@106: with others.
meillo@42: .P
meillo@164: Messages are named by their numeric filename,
meillo@207: but they can have symbolic names, as well.
meillo@207: These are either one of six system-controlled position names
meillo@208: and a shorthand for the range of all messages,
meillo@32: or user-settable group names for arbitrary sets of messages.
meillo@32: These names are called sequences.
meillo@207: Automatically updated position names exist for the
meillo@208: first, last, previous, next, current message, and for the number
meillo@208: one beyond the last message.
meillo@207: (In mmh, the names of these sequences are abbreviated to the
meillo@207: first character.)
meillo@207: User-definded sequences can be bound to the folder containing the
meillo@207: messages (\fIpublic sequences\fP) or to the user's context
meillo@207: (\fIprivate sequences\fP).
meillo@2: .P
meillo@207: The user's \fIprofile\fP is the file that contains his MH configuration.
meillo@47: Default switches for the individual tools can be specified to
meillo@47: adjust them to the user's personal preferences.
meillo@207: These switches will be automatically supplied whenever the specific
meillo@207: tool is invoked.
meillo@164: Additionally, a single command can be linked under different names
meillo@207: with different default values.
meillo@207: Form templates for new messages and replies, as well as format files
meillo@207: to adjust the output of tools are easily exchanged in the profile.
meillo@212: Almost every part of the system can be adjusted to personal preference.
meillo@42: .P
meillo@212: The whole system is well scriptable and extensible.
meillo@207: New MH tools are built out of or on top of existing ones quickly.
meillo@212: MH encourages the user to tailor, extend, and automate the system.
meillo@207: As the MH tool chest was modeled after the Unix tool chest, the
meillo@207: properties of the latter apply to the former as well.
meillo@102: 
meillo@102: 
meillo@102: 
meillo@54: .U2 "Using MH
meillo@53: .P
meillo@209: Many tutorials to using MH
meillo@209: .[
meillo@209: rose sweet mh tutorial
meillo@209: .]
meillo@209: .[
meillo@209: moss jackson user's guide for mh
meillo@209: .]
meillo@209: .[
meillo@209: hegardt mh for beginners
meillo@209: .]
meillo@212: are old, but still they teach the concepts and basics,
meillo@212: which remained unchanged.
meillo@212: Rose and Romine have written an excellent introduction on a more
meillo@212: technical level, with pointers to advanced usage.
meillo@209: .[
meillo@209: rose romine real work
meillo@209: .]
meillo@212: For a more recent document, it is strongly recommended to have
meillo@212: a look at the \fIMH Book\fP,
meillo@54: .[ [
meillo@54: peek mh book
meillo@54: .], Part II]
meillo@212: especially at its online version.
meillo@27: .P
meillo@212: Following here is a sample mail handling session with mmh.
meillo@212: Details might vary to MH and nmh but the look and feel is the same.
meillo@82: 
meillo@202: .so input/mh-session
meillo@27: 
meillo@27: 
meillo@131: .H1 "nmh
meillo@2: .P
meillo@49: In order to understand the condition, goals and dynamics of a project,
meillo@106: one needs to know the reasons behind them.
meillo@212: This section gives background information.
meillo@53: .P
meillo@197: MH predates the Internet;
meillo@212: it comes from times before networking was universal;
meillo@49: it comes from times when emailing was small, short and simple.
meillo@212: Then, MH grew, spread and adapted to the changes email went through.
meillo@212: Its core concepts, however, remained the same.
meillo@106: During the eighties, students at UCI actively worked on MH.
meillo@164: They added new features and optimized the code for the systems
meillo@164: popular at that time.
meillo@212: This was in times before POSIX and ANSI C.
meillo@49: As large parts of the code stem from this time, today's nmh source code
meillo@49: still contains many ancient parts.
meillo@51: BSD-specific code and constructs tailored for hardware of that time
meillo@49: are frequent.
meillo@2: .P
meillo@212: Nmh started about one decade after the POSIX and ANSI C standards were
meillo@212: released.
meillo@212: A more modern coding style entered the code base but still
meillo@212: a part of the developers were ``of the old type''.
meillo@212: The developer base became more diverse,
meillo@212: thus broadening the range of different coding styles.
meillo@49: Programming practices from different decades merged in the project.
meillo@51: As several peers added code, the system became more a conglomeration
meillo@51: of single tools rather than a homogeneous of-one-cast mail system.
meillo@212: For that, leadership would have been necessary.
meillo@212: Nevertheless, MH's basic concepts held the project together.
meillo@8: They were mostly untouched throughout the years.
meillo@8: .P
meillo@212: Though clearly separated on the surface
meillo@212: \(en as a collection of small, separate programs \(en
meillo@212: the source code turns out to be fairly interwoven.
meillo@212: Multiple separate components are compiled into a program
meillo@51: for efficiency reasons.
meillo@212: This leads to intricate innards.
meillo@8: .P
meillo@212: It is visible in nmh that
meillo@212: the advent of MIME raised the complexity of email by a magnitude.
meillo@212: The MIME-related parts are the most complex ones.
meillo@106: It is also visible that MIME support was added on top of the old MH core.
meillo@51: MH's tool chest style made this easily possible and encourages
meillo@106: such approaches, but unfortunately, it led to duplicated functions
meillo@212: and half-hearted implementation of concepts.
meillo@49: .P
meillo@212: To provide backward-compatibility, it is a common understanding
meillo@212: in the nmh community to not change the default settings.
meillo@212: In consequence, users need to activate modern features explicitly
meillo@47: to be able to use them.
meillo@212: The ancient style in which fresh nmh setups remain to appear
meillo@212: causes difficulties for new users, as modern email features require
meillo@212: additional configuration.
meillo@212: The small but mature community around nmh, however, needs little change
meillo@106: as they have had their convenient setups for decades.
meillo@8: 
meillo@8: 
meillo@27: .H1 "mmh
meillo@28: .P
meillo@49: I started to work on my experimental version in October 2011,
meillo@197: basing my work on nmh version \fInmh-1.3-dev\fP.
meillo@197: At that time no more than three commits were made to nmh
meillo@212: since the beginning of 2011, the latest one being
meillo@212: .Ci a01a41d031c796b526329a4170eb23f0ac93b949 ,
meillo@212: commited on 2011-04-13.
meillo@53: In December, when I announced my work in progress on the
meillo@53: nmh-workers mailing list,
meillo@42: .[
meillo@51: nmh-workers mmh announce December
meillo@42: .]
meillo@197: nmh's community became active, all of a sudden.
meillo@49: This movement was heavily pushed by Paul Vixie's ``edginess'' comment.
meillo@42: .[
meillo@42: nmh-workers vixie edginess
meillo@42: .]
meillo@53: After long years of stagnation, nmh became actively developed again.
meillo@197: Hence, while I was working on mmh, the community was working on nmh,
meillo@212: in parallel but unrelated.
meillo@28: .P
meillo@53: The name \fImmh\fP may stand for \fImodern mail handler\fP,
meillo@53: because the project tries to modernize nmh.
meillo@53: Personally however, I prefer to call mmh \fImeillo's mail handler\fP,
meillo@207: emphasizing that the project is my version of nmh,
meillo@207: following my visions and preferences.
meillo@42: (My login name is \fImeillo\fP.)
meillo@53: This project model was inspired by \fIdwm\fP,
meillo@42: which is Anselm Garbe's personal window manager \(en
meillo@42: targeted to satisfy Garbe's personal needs whenever conflicts appear.
meillo@227: Dwm has retained its lean elegance and its focused character,
meillo@227: .[
meillo@227: dwm ohloh
meillo@227: .]
meillo@227: whereas its community-driven predecessor \fIwmii\fP had grown
meillo@227: fat over time.
meillo@227: .[
meillo@227: wmii ohloh
meillo@227: .]
meillo@53: The development of mmh should remain focused.
meillo@27: 
meillo@45: 
meillo@27: .U2 "Motivation
meillo@27: .P
meillo@207: MH is the most important of very few email systems in a tool chest style.
meillo@51: Tool chests are powerful because they can be perfectly automated and
meillo@212: extended.
meillo@212: They allow the implementation of arbitrary kinds of front-ends
meillo@212: on top of the tool chest quickly and without internal knowledge.
meillo@106: Additionally, tool chests are easier to maintain than monolithic
meillo@43: programs.
meillo@227: .[ [
meillo@227: gancarz unix phil
meillo@227: .], p. 14]
meillo@212: MH-like email tool chests should be kept alive as they fill a market
meillo@212: niche by providing conceptional elegance and unique scripting qualities.
meillo@212: Mmh tries to create a modern and convenient entry point to MH-like
meillo@212: systems for new and interested users.
meillo@43: .P
meillo@51: The mmh project is motivated by deficits of nmh and
meillo@212: by my wish for general changes.
meillo@212: At the time the mmh project started, nmh had not yet adjusted to
meillo@212: modern emailing needs well enough.
meillo@45: The default setup was completely unusable for modern emailing.
meillo@45: Too much setup work was required.
meillo@212: Several modern features were already available,
meillo@212: but the community did not want to have them active by default.
meillo@212: Mmh is my way to change this.
meillo@45: .P
meillo@212: In my eyes, MH's concepts could be exploited better and
meillo@212: the style of the tools could be improved.
meillo@212: Both would simplify and generalize the system, providing cleaner
meillo@212: interfaces and greater software leverage at the same time.
meillo@212: Mmh is my way to demonstrate this.
meillo@45: .P
meillo@212: In providing multiple parts of the email system, nmh can hardly
meillo@45: compete with the large specialized projects that focus
meillo@212: on one of the components only.
meillo@212: The situation could be improved by concentrating the development power
meillo@51: on the most unique part of MH and letting the user pick his preferred
meillo@45: set of other mail components.
meillo@45: Today's pre-packaged software components encourage this model.
meillo@212: Mmh is my way to provide this.
meillo@45: .P
meillo@197: It is worthwhile to fork nmh for the development of mmh,
meillo@197: because the two projects focus on different goals and differ in
meillo@197: fundamental questions.
meillo@106: The nmh community's reluctance regarding change conflicts
meillo@106: with my strong desire for it.
meillo@207: .[
meillo@207: nmh-workers schnalke understanding nmh
meillo@207: .]
meillo@212: In developing a separate experimental version, new approaches can
meillo@43: easily be tried out without the need to discuss changes beforehand.
meillo@43: In fact, revolutionary changes are hardly possible otherwise.
meillo@43: .P
meillo@117: The mmh project provides the basis on which the aforementioned
meillo@117: ideas can be implemented and demonstrated,
meillo@164: without the need to change the nmh project or its community.
meillo@43: Of course, the results of the mmh project shall improve nmh, in the end.
meillo@159: By no means it is my intent to work against the nmh project.
meillo@117: 
meillo@27: 
meillo@27: .U2 "Target Field
meillo@27: .P
meillo@45: Any effort needs to be targeted towards a specific goal
meillo@45: in order to be successful.
meillo@197: Therefore, a description of an imagined typical mmh user follows.
meillo@212: Actually, as mmh is my personal version of MH,
meillo@212: this is sort of a description of myself.
meillo@212: Developing software for one's own is a reliable way to produce software
meillo@197: that matches the user's desires.
meillo@45: .P
meillo@197: The target user of mmh likes Unix and its philosophy.
meillo@197: He appreciates to use programs that are conceptionally appealing.
meillo@197: He is familiar with the command line and enjoys its power.
meillo@197: He is capable of shell scripting and wants to improve his
meillo@27: productivity by scripting the mail system.
meillo@197: He uses modern email features, such as attachments,
meillo@169: non-ASCII text, digital signatures and message encryption in a natural way.
meillo@212: He is able to set up mail system components
meillo@212: and likes to pick the ones he prefers.
meillo@197: He has a reasonably modern operating system that complies to the
meillo@164: POSIX and ANSI C standards.
meillo@27: .P
meillo@197: The typical user invokes mmh commands directly in an interactive
meillo@212: shell session, even on workstations where graphical front-ends could
meillo@212: be added.
meillo@197: Likely, he runs his mail setup on a server machine,
meillo@197: to which he connects via ssh.
meillo@212: He might automate mail processing with mmh tools
meillo@212: but definitely he uses the tools to build better tools.
meillo@212: In any case, he wants to have the flexibility to change
meillo@197: his setup to suit his needs.
meillo@8: .P
meillo@197: The typical mmh user is a programmer.
meillo@212: He likes to, occasionally, make use of the opportunity of free software
meillo@212: by putting hands on and getting involved in software he uses.
meillo@197: In consequence, he likes small and clean code bases and cares for
meillo@197: code quality.
meillo@197: In general, he believes that:
meillo@8: .BU
meillo@197: The elegance of source code is most important.
meillo@8: .BU
meillo@197: Concepts are more important than concrete implementations.
meillo@8: .BU
meillo@197: Code optimizations for anything but readability should be avoided.
meillo@8: .BU
meillo@212: Removed code is debugged code.
meillo@212: .BU
meillo@45: Having a lot of choice is bad.
meillo@8: 
meillo@197: 
meillo@212: .U2 "Goals of the mmh Project
meillo@128: .IP "Streamlining
meillo@87: Mmh should be stripped down to its core, which is the user agent (MUA).
meillo@117: The feature set should be distilled to the indispensable ones,
meillo@171: effectively removing corner cases.
meillo@173: Parts that do not add to the main task of being a conceptionally
meillo@187: appealing user agent should be removed.
meillo@212: This includes the mail transfer and mail retrieval facilities.
meillo@48: Choice should be reduced to the main options.
meillo@131: All tools should be tightly shaped.
meillo@48: .IP "Modernizing
meillo@48: Mmh's feature set needs to become more modern.
meillo@212: Better support for attachments, digital signatures, and message
meillo@212: encryption should be added.
meillo@159: MIME support should be integrated deeper and more naturally.
meillo@48: The modern email features need to be readily available, out-of-the-box.
meillo@212: On the other hand, obsolete facilities can be dropped out and
meillo@212: ancient technologies need not be further supported.
meillo@212: The available concepts should be expanded as far as possible.
meillo@131: A small set of concepts should recur consistently.
meillo@131: .IP "Styling
meillo@212: Mmh's source code should be updated to modern standards.
meillo@48: Standardized library functions should replace non-standard versions
meillo@48: whenever possible.
meillo@117: Code should be separated into distinct modules when feasible.
meillo@48: Time and space optimizations should to be replaced by
meillo@48: clear and readable code.
meillo@48: A uniform programming style should prevail.
meillo@117: The whole system should appear to be of-one-style;
meillo@117: it should feel like being cast as one.