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1 .RN 1
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2
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3 .H0 "Introduction
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4 .P
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5 MH is a set of mail handling tools with a common concept, similar to
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6 the Unix tool chest, which is a set of file handling tools with a common
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7 concept. \fInmh\fP is the currently most popular implementation of an
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8 MH-like mail handling system.
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9 This thesis describes an experimental version of nmh, named \fImmh\fP.
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10 .P
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11 This chapter introduces MH, its history, concepts and how it is used.
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12 It describes nmh's code base and community to give the reader
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13 a better understanding of the state from which mmh started off.
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14 Further more, this chapter outlines the mmh project itself,
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15 describing the motivation for it and its goals.
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16
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17
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18 .H1 "MH \(en the Mail Handler
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19 .P
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20 MH is a conceptual email system design and its concrete implementation.
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21 Notably, MH had started as a design proposal at RAND Corporation,
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22 where the first implementation followed later.
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23 In spirit, MH is similar to Unix, which
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24 influenced the world more in being a set of system design concepts
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25 than in being a specific software product.
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26 The ideas behind Unix are summarized in the \fIUnix philosophy\fP.
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27 MH follows this philosophy.
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28
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29 .U2 "History
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30 .P
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31 In 1977 at RAND Corporation, Norman Shapiro and Stockton Gaines
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32 had proposed the design
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33 of a new mail handling system, called ``Mail Handler'' (MH),
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34 to superseed RAND's old monolithic ``Mail System'' (MS).
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35 Two years later, in 1979, Bruce Borden took the proposal and implemented a
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36 prototype of MH.
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37 Before the prototype had been available, the concept was
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38 believed to be practically unusable.
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39 But the prototype had proven successful and replaced MS thereafter.
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40 In replacing MS, MH grew to an all-in-one mail system.
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41 .P
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42 In the early Eighties,
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43 the University of California at Irvine (UCI) had started to use MH.
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44 Marshall T. Rose and John L. Romine became the driving force then.
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45 They took over the development and pushed MH forward.
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46 RAND had put the code into the public domain by then.
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47 MH was developed at UCI at the time when the Internet appeared,
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48 when UCB implemented the TCP/IP stack, and when Allman wrote Sendmail.
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49 MH was extended as emailing became more featured.
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50 The development of MH was closely related to the development of email
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51 RFCs. In the advent of MIME, MH was the first implementation of this new
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52 email standard.
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53 .P
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54 In the Nineties, the Internet had become popular and in December 1996,
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55 Richard Coleman initiated the ``New Mail Handler'' (nmh) project.
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56 Nmh is a fork of MH 6.8.3 and bases strongly on the
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57 \fILBL changes\fP by Van Jacobson, Mike Karels and Craig Leres.
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58 Colman intended to modernize MH and improve its portability and
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59 MIME handling capabilities.
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60 This should be done openly within the Internet community.
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61 The development of MH at UCI stopped after the 6.8.4 release in
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62 February 1996, soon after the development of nmh had started.
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63 Today, nmh has almost completely replaced the original MH.
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64 Some systems might still provide old MH, but mainly for historical reasons.
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65 .P
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66 In the last years, the work on nmh was mostly maintenance work.
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67 However, the development revived in December 2011
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68 and stayed busy since then.
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69
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70 .U2 "Concepts
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71 .P
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72 MH consists of a set of tools, each covering a specific task of
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73 email handling, like composing a message, replying to a message,
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74 refiling a message to a different folder, listing the messages in a folder.
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75 All of the programs operate on a common mail storage.
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76 .P
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77 The mail storage consists of \fImail folders\fP (directories) and
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78 \fPmessages\fP (regular files).
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79 Each message is stored in a separate file in the format it had been
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80 received (i.e. transfer format).
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81 The files are named with ascending numbers in each folder.
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82 The specific format of the mail storage characterizes MH in the same way
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83 like the format of the file system characterizes Unix.
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84 .P
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85 MH tools maintain a \fIcontext\fP, which includes the current mail folder.
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86 Processes in Unix have a similar context, containing the current working
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87 directory, for instance. In contrast, the process context is maintained
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88 by the Unix kernel automatically, whereas MH tools need to maintain the MH
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89 context themselves.
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90 The user can have one MH context or multiple ones, he can even share it
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91 with other users.
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92 .P
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93 Messages are named by their numeric filename, but they can have symbolic names,
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94 too. These are either automatically updated
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95 position names like being the next or the last message,
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96 or user-settable group names for arbitrary sets of messages.
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97 These names are called sequences.
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98 Sequences can be bound to the containing folder or to the context.
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99 .P
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100 The user's \fIprofile\fP is a file that contains his MH configuration.
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101 Default switches for the individual tools can be specified to
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102 adjust them to the user's personal preferences.
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103 Multiple versions of the same command with different
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104 default values can also be created very easily.
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105 Form templates for new messages or for replies are easily changeable,
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106 and output is adjustable with format files.
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107 Almost every part of the system can be adjusted to personal preference.
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108 .P
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109 The system is well scriptable and extensible.
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110 New MH tools are built out of or on top of existing ones quickly.
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111 Further more, MH encourages the user to tailor, extend and automate the system.
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112 As the MH tool chest was modeled after the Unix tool chest, the
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113 properties of the latter apply to the former as well.
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114
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115 .U2 "Using MH
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116 .P
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117 It is strongly recommended to have a look at the MH Book,
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118 which introduces well into using MH.
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119 .[ [
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120 peek mh book
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121 .], Part II]
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122 Rose and Romine provide a deeper and more technical
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123 though slightly outdated introduction in only about two dozens pages.
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124 .[
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125 rose romine real work
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126 .]
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127 .P
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128 Following is an example mail handling session.
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129 It uses mmh but is mostly compatible with nmh and old MH.
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130 Details might vary but the look'n'feel is the same.
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131
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132 .VF input/mh-session
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133
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134
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135 .H1 "nmh: Code and Community
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136 .P
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137 In order to understand the condition, goals and dynamics of a project,
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138 one needs to know the reasons.
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139 This section explains the background.
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140 .P
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141 MH predates the Internet, it comes from times before networking was universal,
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142 it comes from times when emailing was small, short and simple.
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143 Then it grew, spread and adopted to the changes email went through.
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144 Its core-concepts, however, remained the same.
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145 During the Eighties students at UCI actively worked on MH.
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146 They added new features and optimized the code for the then popular systems.
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147 All this still was in times before POSIX and ANSI C.
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148 As large parts of the code stem from this time, today's nmh source code
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149 still contains many ancient parts.
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150 BSD-specific code and constructs tailored for hardware of that time
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151 are frequent.
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152 .P
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153 Nmh started about a decade after the POSIX and ANSI C standards had been
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154 established. A more modern coding style entered the code base, but still
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155 a part of the developers came from ``the old days''. The developer
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156 base became more diverse and thus resulted in code of different style.
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157 Programming practices from different decades merged in the project.
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158 As several peers added code, the system became more a conglomeration
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159 of single tools rather than a homogeneous of-one-cast mail system.
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160 Still, the existing basic concepts held it together.
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161 They were mostly untouched throughout the years.
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162 .P
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163 Despite the tool chest approach at the surface \(en a collection
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164 of separate small programs \(en on the source code level
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165 it is much more interweaved.
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166 Several separate components were compiled into one program
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167 for efficiency reasons.
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168 This lead to intricate innards.
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169 Unfortunately, the clear separation on the outside appeared as being
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170 pretty interweaved inside.
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171 .P
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172 The advent of MIME rose the complexity of email by a magnitude.
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173 This is visible in nmh. The MIME-related parts are the most complex ones.
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174 It's also visible that MIME support had been added on top of the old MH core.
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175 MH's tool chest style made this easily possible and encourages
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176 such approaches, but unfortunately, it lead to duplicated functions
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177 and half-hearted implementation of the concepts.
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178 .P
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179 To provide backward-compatibility, it is a common understanding to not
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180 change the default settings.
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181 In consequence, the user needs to activate modern features explicitly
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182 to be able to use them.
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183 This puts a burden on new users, because out-of-the-box nmh remains
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184 in the same ancient style.
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185 If nmh is seen to be a back-end, then this compatibility surely is important.
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186 However, in the same go, new users have difficulties to use nmh for modern
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187 emailing.
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188 The small but matured community around nmh hardly needs much change
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189 as they have their convenient setups since decades.
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190
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191
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192 .H1 "mmh
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193 .P
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194 I started to work on my experimental version in October 2011,
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195 at a time when there were no more than three commits to nmh
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196 since the beginning of the year.
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197 In December, when I announced my work in progress on the
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198 nmh-workers mailing list,
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199 .[
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200 nmh-workers mmh announce December
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201 .]
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202 nmh's community became active, too.
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203 This movement was heavily pushed by Paul Vixie's ``edginess'' comment.
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204 .[
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205 nmh-workers vixie edginess
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206 .]
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207 After long years of stagnation, nmh became actively developed again.
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208 Hence, while I was working on mmh, the community was working on nmh,
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209 in parallel.
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210 .P
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211 The name \fImmh\fP may stand for \fImodern mail handler\fP,
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212 because the project tries to modernize nmh.
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213 Personally however, I prefer to call mmh \fImeillo's mail handler\fP,
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214 emphasizing that the project follows my visions and preferences.
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215 (My login name is \fImeillo\fP.)
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216 This project model was inspired by \fIdwm\fP,
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217 which is Anselm Garbe's personal window manager \(en
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218 targeted to satisfy Garbe's personal needs whenever conflicts appear.
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219 Dwm had retained its lean elegance and its focused character, whereas
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220 its community-driven predecessor \fIwmii\fP had grown fat over time.
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221 The development of mmh should remain focused.
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222
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223
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224 .U2 "Motivation
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225 .P
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226 MH is the most important of very few command line tool chest email systems.
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227 Tool chests are powerful because they can be perfectly automated and
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228 extended. They allow arbitrary kinds of front-ends to be
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229 implemented on top of them quickly and without internal knowledge.
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230 Additionally, tool chests are much better to maintain than monolithic
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231 programs.
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232 As there are few tool chests for emailing and as MH-like ones are the most
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233 popular among them they should be developed further.
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234 This keeps their
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235 conceptional elegance and unique scripting qualities available to users.
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236 Mmh will create a modern and convenient entry point to MH-like systems
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237 for new and interested users.
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238 .P
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239 The mmh project is motivated by deficits of nmh and
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240 my wish for general changes, combined
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241 with the nmh community's reluctancy to change.
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242 .P
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243 nmh hadn't adjusted to modern emailing needs well enough.
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244 The default setup was completely unusable for modern emailing.
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245 Too much setup work was required.
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246 Several modern features were already available but the community
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247 didn't wanted to have them as default.
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248 mmh is a way to change this.
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249 .P
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250 In my eyes, MH's concepts could be exploited even better and
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251 the style of the tools could be improved. Both would simplify
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252 and generalize the system, providing cleaner interfaces and more
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253 software leverage at the same time.
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254 mmh is a way to demonstrate this.
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255 .P
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256 In providing several parts of an email system, nmh can hardly
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257 compete with the large specialized projects that focus
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258 on only one of the components.
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259 The situation can be improved by concentrating the development power
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260 on the most unique part of MH and letting the user pick his preferred
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261 set of other mail components.
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262 Today's pre-packaged software components encourage this model.
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263 mmh is a way to go for this approach.
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264 .P
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265 It's worthwhile to fork nmh for the development of mmh, because
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266 the two projects focus on different goals and differ in fundamental questions.
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267 The nmh community's reluctance to change conflicts
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268 with my strong will to change.
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269 In developing a separate experimental version new approaches can
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270 easily be tried out without the need to discuss changes beforehand.
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271 In fact, revolutionary changes are hardly possible otherwise.
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272 .P
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273 The mmh project provides the basis to implemented and demonstrated
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274 the listed ideas without the need to change nmh or its community.
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275 Of course, the results of the mmh project shall improve nmh, in the end.
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276
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277 .U2 "Target Field
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278 .P
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279 Any effort needs to be targeted towards a specific goal
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280 in order to be successful.
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281 Following is a description of the imagined typical mmh user.
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282 mmh should satisfy his needs.
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283 .\" XXX Remove the next sentence?
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284 Actually, as mmh is my personal version of MH, this is a description
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285 of myself.
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286 .P
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287 The target user of mmh likes Unix and its philosophy.
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288 He likes to use programs that are conceptionally appealing.
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289 He's familiar with the command line and enjoys its power.
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290 He is at least capable of shell scripting and wants to improve his
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291 productivity by scripting the mail system.
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292 He naturally uses modern email features, like attachments,
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293 non-ASCII text, and digital cryptography.
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294 He is able to setup email system components besides mmh,
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295 and actually likes the choice to pick the ones he prefers.
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296 He has a reasonably modern system that complies to standards,
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297 like POSIX and ANSI C.
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meillo@27
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298 .P
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meillo@48
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299 The typical user invokes mmh commands directly in an interactive
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meillo@48
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300 shell session, but as well, he uses them to automate mail handling tasks.
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meillo@48
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301 Likely, he runs his mail setup on a server machine, to which he connects
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meillo@48
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302 via ssh. He might also have local mmh installations on his workstations,
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meillo@51
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303 but does rather not rely on graphical front-ends. He definitely wants
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meillo@48
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304 to be flexible and thus be able to change his setup to suite his needs.
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meillo@8
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305 .P
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meillo@48
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306 The typical mmh user is a programmer himself.
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meillo@48
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307 He likes to, occasionally, take the opportunity of Free Software to put
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meillo@48
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308 hands on and get involved in the software he uses.
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meillo@48
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309 Hence, he likes small and clean code bases and he cares for code quality.
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meillo@48
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310 In general, he believes that:
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meillo@8
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311 .BU
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meillo@48
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312 Elegance \(en i.e. simplicity, clarity and generality \(en
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meillo@48
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313 is most important.
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meillo@8
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314 .BU
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meillo@48
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315 Concepts are more important than the concrete implementation.
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meillo@8
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316 .BU
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meillo@48
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317 Code optimizations for anything but readability should be avoided
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meillo@48
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318 if possible.
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meillo@8
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319 .BU
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meillo@45
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320 Having a lot of choice is bad.
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meillo@48
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321 .BU
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meillo@48
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322 Removed code is debugged code.
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meillo@8
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323
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meillo@48
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324 .U2 "Goals
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meillo@45
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325 .P
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meillo@45
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326 The general goals for the mmh project are the following:
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meillo@48
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327 .IP "Stream-lining
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meillo@87
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328 Mmh should be stripped down to its core, which is the user agent (MUA).
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meillo@48
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329 The feature set should be distilled to the ones really needed,
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meillo@48
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330 effectively removing corner-cases.
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meillo@53
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331 Parts that don't add to the main task of being a conceptionally
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meillo@53
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332 appealing MUA should be removed.
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meillo@87
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333 This includes, the mail submission and mail retrieval facilities.
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meillo@48
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334 Choice should be reduced to the main options.
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meillo@48
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335 .IP "Modernizing
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meillo@48
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336 Mmh's feature set needs to become more modern.
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meillo@48
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337 Better support for attachment and digital cryptography needs to be added.
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meillo@48
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338 MIME support needs to be integrated deeper and more naturally.
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meillo@48
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339 The modern email features need to be readily available, out-of-the-box.
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meillo@48
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340 And on the other hand,
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meillo@48
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341 bulletin board support and similar obsolete facilities need to be dropped
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meillo@48
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342 out.
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meillo@48
|
343 Likewise, ancient technologies, like hardcopy terminals, should not
|
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meillo@48
|
344 be supported any further.
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|
meillo@48
|
345 .IP "Code style
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meillo@48
|
346 Mmh's source code needs to be updated to modern standards.
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meillo@48
|
347 Standardized library functions should replace non-standard versions
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|
meillo@48
|
348 whenever possible.
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meillo@48
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349 Code should be separated into distinct modules when possible.
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meillo@48
|
350 Time and space optimizations should to be replaced by
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meillo@48
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351 clear and readable code.
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meillo@48
|
352 A uniform programming style should prevail.
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meillo@51
|
353 .IP "Homogeneity
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meillo@48
|
354 The available concepts need to be expanded as far as possible.
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meillo@48
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355 A small set of concepts should prevail thoroughly throughout the system.
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meillo@48
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356 The whole system should appear to be of-one-style.
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meillo@48
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357 It should feel like being cast as one.
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