1 \clearpage

2 \chapter*{Preface}

3 \addcontentsline{toc}{section}{Preface}

4

5 This thesis is about \masqmail, a small mail transfer agent for workstations and home networks. In October 2007 I had chosen \masqmail\ for my machines because of its small size though it was a ``real'' mail transfer agent. \masqmail\ served me well since then and I have found no reasons to change.

6 \index{masqmail}

7

8 Unfortunately, the \masqmail\ package in \name{Debian}, which is my preferred \NAME{GNU}/Li\-nux distribution, is unmaintained since the beginning of 2008. Unmaintained packages are likely to get dropped out of a distribution if critical bugs appear in them. Although \masqmail\ had no critical bugs, this was a situation I definitely wanted to prevent.

9 \index{Debian!masqmail package}

10

11 Using my diploma thesis as a ``power-start'' for maintaining and developing \masqmail\ in the future was a great idea. As it came to my mind I knew this is the thing I \emph{wanted} to do. --- I did it! :-)

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13 \quad

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15 The overall goal of this document is to revive \masqmail\ in usage and development. \masqmail\ was not developed further in the last five years although the world of email has changed during this time. Hence quite some work needed to be done.

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17 I decided to start at the basis and analyze the environment and \masqmail\ throughout to end up in concrete plans of what should be done and how it should be done to turn \masqmail\ into a modern mail transfer agent again.

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19 The actual implementation of the proposed changes will follow-up this thesis. Here solutions are identified, described, discussed, and recommended but not implemented. I have been working in the code and have fixed bugs during the time I worked on the thesis, though.

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21 \quad

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23 This document is primary written with an audience of \masqmail\ developers and developers of other mail transfer agents in mind. But users of \masqmail\ and everyone who is interested in email systems in general may find this thesis an interesting literature, too.

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25 However, at least basic knowledge about Unix and C programming is a prerequisite for chapters three, four, and five. \person{Kernighan} and \person{Pike}'s ``The \NAME{UNIX} Programming Environment'' \cite{kernighan84} is a valuable source to gain information about Unix. Programming in the C language is best learned from \person{Kernighan} and \person{Ritchie}'s ``The C Programming Language'' \cite{k&r}.

26 \index{c}

27 \index{Unix}

28

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34

35

36 \section*{Organization}

37

38 The document consists of six chapters, each covering a delimited part of the overall topic and building upon the content and results of previous chapters. The first three chapters lead into the topic and create a solid base where the second part builds upon. The chapters four and five form the central part of the thesis as they focus on \masqmail.

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40 Chapter 1 \textbf{introduces} \masqmail\ to the reader. It presents the properties, goals, advantages, and problems of the program. Basic concepts of the email technology are also described and later assumed to be known.

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42 Chapter 2 \textbf{analyzes the market} of electronic communication and email. This chapter gives sound reasons for the sense of future development of \masqmail\ by showing that email will remain an important technology in the future. It tries to identify future trends, too.

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44 Chapter 3 \textbf{deals with mail transfer agents} (\MTA{}s) which are the most important entities of the email transport structure. \MTA{}s are defined, classified, and the most important ones are presented and compared.

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46 Chapter 4 \textbf{focuses on \masqmail's present and future}. It is the core of the thesis. Requirements are identified and lead to a list of pending work tasks. Then possible strategies for future development are discussed.

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48 Chapter 5 \textbf{describes improvement plans} which are based on decisions in chapter four, in more detail. A proposed architecture for a redesigned \masqmail\ is presented, too.

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50 Chapter 6 \textbf{summarizes} the most important results and closes the thesis.

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55

56

57 \section*{Conventions}

58 %TODO: check it!

59 The following typographic conventions are used in this thesis:

60

61 \begin{enumerate}

62 \item \emph{Italic shape} is used to emphasize text, to introduce new terms, and for names, including product, host, and user names, as well as email addresses.

63

64 \item For names of persons \textsc{Small Caps} are used.

65

66 \item File and path names, contents of files, and output from programs are displayed in \texttt{Typewriter font}.

67 \end{enumerate}

68

69 References to external resources are marked using one of three styles, distinguished by the type of resource.

70

71 \begin{enumerate}

72 \item References to books, articles, and documents of similar kind, look like this: \cite{kernighan84}. The letters represent the author(s) (here \person{Kernighan} and \person{Pike}), while the number represents the year of publication (here 1984).

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74 \item Websites are different from documents as they are less some text written by some author but more a place where information is gathered. Website may also change from time to time, thus the date of access is given to indicate the version to which was referred. References to websites have such appearance: \citeweb{masqmail:homepage}.

75

76 \item \name{Request for Comments} are those documents that define the Internet. They are referenced directly by their unique number. For instance: \RFC\,821.

77 \end{enumerate}

78 \index{rfc}

79

80 The Bibliography is located at the end of the thesis. It also includes a list of the relevant \RFC{}s and how they can be retrieved.

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82

83

84

85

86 \section*{Acknowledgments}

87

88 First, I want to thank \person{Oliver Kurth} for writing \masqmail; I build upon his work. My second thanks goes to professor \person{Markus Sch\"affter}, my advisor. He was the one who made this thesis possible by putting faith in me and this topic. I very much enjoyed the time with him.

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90 I thank \person{Christian Langbein} and professor \person{Volkmar Kese} for teaching me important lessons about structure. You are so right, it is all about: structure, structure, structure.

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92 My \person{Dad} and my friend \person{Julian Forster} took time for me so I could explain various parts of the thesis to them; this was important, thanks. \person{James Stenard} was of great help in questions about the English language, thanks. \person{Roger Schietzel} double-checked all web addresses and \NAME{ISBN}s for validity, thanks for covering this bulky task.

93

94 \person{Henry Atting},

95 \person{Joachim Breitner},

96 \person{Marc Geis},

97 \person{Jochen Roth},

98 and \person{Hans-J\"org Schaaf}

99 (in alphabetical order) had a look at my thesis and returned comments and suggestions---each one was valuable. Thank you all.

100

101 Not to forget is everyone who discussed with me on mailing lists and in private communication, and my family for backing me.

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103 There is also an institution that needs to be praised: The \name{W\"urttembergische Landesbibliothek} in Stuttgart; it was the most productive place to work and the most impressive one, too.

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105 \quad

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107 But the most support I did receive from \person{Lydi}. I am deeply grateful for your patience and sacrifice during the last months; for your motivation and encouragement; and for the ease I found in your arms. \quad Thank you!

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110 \vspace{6ex}

111 \hspace*{27em}\textit{markus schnalke}

112