.RN 1

.H0 "Introduction
.P
MH is a set of mail handling tools with a common concept, similar to
the Unix tool chest, which is a set of file handling tools with a common
concept. \fInmh\fP is the currently most popular implementation of an
MH-like mail handling system.
This thesis describes an experimental version of nmh, named \fImmh\fP.
.P
This chapter introduces MH, its history, concepts and how it is used.
It describes nmh's code base and community to give the reader
a better understanding of the state from which mmh started off.
Further more, this chapter outlines the mmh project itself,
describing the motivation for it and its goals.


.H1 "MH \(en the Mail Handler
.P
MH is a conceptual email system design and its concrete implementation.
Notably, MH had started as a design proposal at RAND Corporation,
where the first implementation followed later.
In spirit, MH is similar to Unix, which
influenced the world more in being a set of system design concepts
than in being a specific software product.
The ideas behind Unix are summarized in the \fIUnix philosophy\fP.
MH follows this philosophy.

.U2 "History
.P
In 1977 at RAND Corporation, Norman Shapiro and Stockton Gaines
had proposed the design
of a new mail handling system, called ``Mail Handler'' (MH),
to superseed RAND's old monolithic ``Mail System'' (MS).
Two years later, in 1979, Bruce Borden took the proposal and implemented a
prototype of MH.
Before the prototype had been available, the concept was
believed to be practically unusable.
But the prototype had proven successful and replaced MS thereafter.
In replacing MS, MH grew to an all-in-one mail system.
.P
In the early Eighties,
the University of California at Irvine (UCI) had started to use MH.
They also took over its development and pushed MH forward.
Marshall T. Rose and John L. Romine became the driving force then.
This was the time when the Internet appeared, when UCB implemented
the TCP/IP stack, and when Allman wrote Sendmail.
MH was extended as emailing became more featured.
The development of MH was closely related to the development of email
RFCs. In the advent of MIME, MH was the first implementation of this new
email standard.
.P
In the Nineties, MH had been moved into the public domain, making it
attractive to Free Software developers.
The Internet had became popular and in December 1996,
Richard Coleman initiated the ``New Mail Handler'' (nmh) project.
The project is a fork of MH 6.8.3 and bases strongly on the
\fILBL changes\fP by Van Jacobson, Mike Karels and Craig Leres.
Colman intended to modernize MH and improve its portability and
MIME handling capabilities.
This should be done openly within the Internet community.
The development of MH at UCI stopped after the 6.8.4 release in
February 1996, soon after the development of nmh had started.
Today, nmh almost completely replaces the original MH.
Some systems might still provide old MH, but mainly for historical reasons.
.P
In the last years, the work on nmh was mostly maintenance work.
However, the development revived in December 2011 and stayed busy since then.

.U2 "Concepts
.P
MH consists of a set of tools, each covering a specific task of
email handling, like composing a message, replying to a message,
refiling a message to a different folder, listing the messages in a folder.
All of the programs operate on a common mail storage.
.P
The mail storage consists of \fImail folders\fP (directories) and
\fPmessages\fP (regular files).
Each message is stored in a separate file in the format it had been
received (i.e. transfer format).
The files are named with ascending numbers in each folder.
The specific format of the mail storage characterizes MH in the same way
like the format of the file system characterizes Unix.
.P
MH tools maintain a \fIcontext\fP, which includes the current mail folder.
Processes in Unix have a similar context, containing the current working
directory, for instance. In contrast, the process context is maintained
by the Unix kernel automatically, whereas MH tools need to maintain the MH
context themselves.
The user can have one MH context or multiple ones, he can even share it
with other users.
.P
Messages are named by their numeric filename, but they can have symbolic names,
too. These are either automatically updated
position names like being the next or the last message,
or user-settable group names for arbitrary sets of messages.
These names are called sequences.
Sequences can be bound to the containing folder or to the context.
.P
The user's \fIprofile\fP is a file that contains his MH configuration.
Default switches for the individual tools can be specified to
adjust them to the user's personal preferences.
Multiple versions of the same command with different
default values can also be created very easily.
Form templates for new messages or for replies are easily changeable,
and output is adjustable with format files.
Almost every part of the system can be adjusted to personal preference.
.P
The system is well scriptable and extensible.
New MH tools are built out of or on top of existing ones quickly.
Further more, MH encourages the user to tailor, extend and automate the system.
As the MH tool chest was modeled after the Unix tool chest, the
properties of the latter apply to the former as well.

.U2 "Using MH
.P
It is strongly recommended to have a look at the MH Book,
which introduces well into using MH.
.[ [
peek mh book
.], Part II]
Rose and Romine provide a deeper and more technical
though slightly outdated introduction in only about two dozens pages.
.[
rose romine real work
.]
.P
Following is an example mail handling session.
It uses mmh but is mostly compatible with nmh and old MH.
Details might vary but the look'n'feel is the same.
.DS
$ \f(CBinc\fP
Incorporating new mail into inbox...
	
   1+ 2012-05-16 11:16  meillo@dream.home  Hello
   2  2012-05-16 11:17  meillo@dream.home  book
	
$ \f(CBshow\fP
Date:    Wed, 16 May 2012 11:16:00 +0200
To:      meillo
From:    <meillo@dream.home.schnalke.org>
Subject: Hello
	
part       text/plain                  13
mmh is great
	
$ \f(CBnext\fP
Date:    Wed, 16 May 2012 11:17:24 +0200
To:      meillo
From:    <meillo@dream.home.schnalke.org>
Subject: book
	
part       text/plain                  79
Hello meillo,
	
have a look at the ``Daemon book''. You need to read that!
	
foo
	
$ \f(CBrmm 1\fP
	
$ \f(CBscan\fP
   2+ 2012-05-16 11:17  meillo@dream.home  book
	
$
.DE


.H1 "nmh: Code and Community
.P
In order to understand the condition, goals and dynamics of a project,
one needs to know the reasons.
This section explains the background.
.P
MH predates the Internet, it comes from times before networking was universal,
it comes from times when emailing was small, short and simple.
Then it grew, spread and adopted to the changes email went through.
Its core-concepts, however, remained the same.
During the Eighties students at UCI actively worked on MH.
They added new features and optimized the code for the then popular systems.
All this still was in times before POSIX and ANSI C.
As large parts of the code stem from this time, today's nmh source code
still contains many ancient parts.
BSD-specific code and constructs tailored for hardware of that time
are frequent.
.P
Nmh started about a decade after the POSIX and ANSI C standards had been
established. A more modern coding style entered the code base, but still
a part of the developers came from ``the old days''. The developer
base became more diverse and thus resulted in code of different style.
Programming practices from different decades merged in the project.
As several peers added code, the system became more a conglomeration
of single tools rather than a homogeneous of-one-cast mail system.
Still, the existing basic concepts held it together.
They were mostly untouched throughout the years.
.P
Despite the tool chest approach at the surface \(en a collection
of separate small programs \(en on the source code level
it is much more interweaved.
Several separate components were compiled into one program
for efficiency reasons.
This lead to intricate innards.
Unfortunately, the clear separation on the outside appeared as being
pretty interweaved inside.
.P
The advent of MIME rose the complexity of email by a magnitude.
This is visible in nmh. The MIME-related parts are the most complex ones.
It's also visible that MIME support had been added on top of the old MH core.
MH's tool chest style made this easily possible and encourages
such approaches, but unfortunately, it lead to duplicated functions
and half-hearted implementation of the concepts.
.P
To provide backward-compatibility, it is a common understanding to not
change the default settings.
In consequence, the user needs to activate modern features explicitly
to be able to use them.
This puts a burden on new users, because out-of-the-box nmh remains
in the same ancient style.
If nmh is seen to be a back-end, then this compatibility surely is important.
However, in the same go, new users have difficulties to use nmh for modern
emailing.
The small but matured community around nmh hardly needs much change
as they have their convenient setups since decades.


.H1 "mmh
.P
I started to work on my experimental version in October 2011,
at a time when there were no more than three commits to nmh
since the beginning of the year.
In December, when I announced my work in progress on the
nmh-workers mailing list,
.[
nmh-workers mmh announce December
.]
nmh's community became active, too.
This movement was heavily pushed by Paul Vixie's ``edginess'' comment.
.[
nmh-workers vixie edginess
.]
After long years of stagnation, nmh became actively developed again.
Hence, while I was working on mmh, the community was working on nmh,
in parallel.
.P
The name \fImmh\fP may stand for \fImodern mail handler\fP,
because the project tries to modernize nmh.
Personally however, I prefer to call mmh \fImeillo's mail handler\fP,
emphasizing that the project follows my visions and preferences.
(My login name is \fImeillo\fP.)
This project model was inspired by \fIdwm\fP,
which is Anselm Garbe's personal window manager \(en
targeted to satisfy Garbe's personal needs whenever conflicts appear.
Dwm had retained its lean elegance and its focused character, whereas
its community-driven predecessor \fIwmii\fP had grown fat over time.
The development of mmh should remain focused.


.U2 "Motivation
.P
MH is the most important of very few command line tool chest email systems.
Tool chests are powerful because they can be perfectly automated and
extended. They allow arbitrary kinds of front-ends to be
implemented on top of them quickly and without internal knowledge.
Additionally, tool chests are much better to maintain than monolithic
programs.
As there are few tool chests for emailing and as MH-like ones are the most
popular among them they should be developed further.
This keeps their
conceptional elegance and unique scripting qualities available to users.
Mmh will create a modern and convenient entry point to MH-like systems
for new and interested users.
.P
The mmh project is motivated by deficits of nmh and
my wish for general changes, combined
with the nmh community's reluctancy to change.
.P
nmh hadn't adjusted to modern emailing needs well enough.
The default setup was completely unusable for modern emailing.
Too much setup work was required.
Several modern features were already available but the community
didn't wanted to have them as default.
mmh is a way to change this.
.P
In my eyes, MH's concepts could be exploited even better and
the style of the tools could be improved. Both would simplify
and generalize the system, providing cleaner interfaces and more
software leverage at the same time.
mmh is a way to demonstrate this.
.P
In providing several parts of an email system, nmh can hardly
compete with the large specialized projects that focus
on only one of the components.
The situation can be improved by concentrating the development power
on the most unique part of MH and letting the user pick his preferred
set of other mail components.
Today's pre-packaged software components encourage this model.
mmh is a way to go for this approach.
.P
It's worthwhile to fork nmh for the development of mmh, because
the two projects focus on different goals and differ in fundamental questions.
The nmh community's reluctance to change conflicts
with my strong will to change.
In developing a separate experimental version new approaches can
easily be tried out without the need to discuss changes beforehand.
In fact, revolutionary changes are hardly possible otherwise.
.P
The mmh project provides the basis to implemented and demonstrated
the listed ideas without the need to change nmh or its community.
Of course, the results of the mmh project shall improve nmh, in the end.

.U2 "Target Field
.P
Any effort needs to be targeted towards a specific goal
in order to be successful.
Following is a description of the imagined typical mmh user.
mmh should satisfy his needs.
.\" XXX  Remove the next sentence?
Actually, as mmh is my personal version of MH, this is a description
of myself.
.P
The target user of mmh likes Unix and its philosophy.
He likes to use programs that are conceptionally appealing.
He's familiar with the command line and enjoys its power.
He is at least capable of shell scripting and wants to improve his
productivity by scripting the mail system.
He naturally uses modern email features, like attachments,
non-ASCII text, and digital cryptography.
He is able to setup email system components besides mmh,
and actually likes the choice to pick the ones he prefers.
He has a reasonably modern system that complies to standards,
like POSIX and ANSI C.
.P
The typical user invokes mmh commands directly in an interactive
shell session, but as well, he uses them to automate mail handling tasks.
Likely, he runs his mail setup on a server machine, to which he connects
via ssh. He might also have local mmh installations on his workstations,
but does rather not rely on graphical front-ends. He definitely wants
to be flexible and thus be able to change his setup to suite his needs.
.P
The typical mmh user is a programmer himself.
He likes to, occasionally, take the opportunity of Free Software to put
hands on and get involved in the software he uses.
Hence, he likes small and clean code bases and he cares for code quality.
In general, he believes that:
.BU
Elegance \(en i.e. simplicity, clarity and generality \(en
is most important.
.BU
Concepts are more important than the concrete implementation.
.BU
Code optimizations for anything but readability should be avoided
if possible.
.BU
Having a lot of choice is bad.
.BU
Removed code is debugged code.

.U2 "Goals
.P
The general goals for the mmh project are the following:
.IP "Stream-lining
Mmh should be stripped down to its core, which is the MUA part of emailing.
The feature set should be distilled to the ones really needed,
effectively removing corner-cases.
Parts that don't add to the main task of being a conceptionally
appealing MUA should be removed.
This includes, the MTA and MRA facilities.
Choice should be reduced to the main options.
.IP "Modernizing
Mmh's feature set needs to become more modern.
Better support for attachment and digital cryptography needs to be added.
MIME support needs to be integrated deeper and more naturally.
The modern email features need to be readily available, out-of-the-box.
And on the other hand,
bulletin board support and similar obsolete facilities need to be dropped
out.
Likewise, ancient technologies, like hardcopy terminals, should not
be supported any further.
.IP "Code style
Mmh's source code needs to be updated to modern standards.
Standardized library functions should replace non-standard versions
whenever possible.
Code should be separated into distinct modules when possible.
Time and space optimizations should to be replaced by
clear and readable code.
A uniform programming style should prevail.
.IP "Homogeneity
The available concepts need to be expanded as far as possible.
A small set of concepts should prevail thoroughly throughout the system.
The whole system should appear to be of-one-style.
It should feel like being cast as one.