1 \chapter{Introduction}

2 \label{chap:introduction}

3

4 << say what you want to say >>

5

6 << the overall goal of the document >>

7

8

9

10 \section{What's an MTA?}

11

12 The basic job of a \mta\ is to transport mail from senders to recipients. This is the definition of such kind of software, and this is how \MTA{}s are generally seen \cite[page 19]{dent04} \cite[pages 3-5]{hafiz05}.

13

14 An \MTA\ therefore needs at least a mail receiving facility and a mail sending facility.

15

16 << structure diagram of an MTA (and of masqmail) >>

17

18

19

20

21

22 \section{The \masqmail\ project}

23 \label{sec:masqmail}

24

25 << about masqmail (some history) >>

26

27 (include history of email, definition of MTA and sendmail-compatibility in text)

28

29 The \masqmail\ program was written by Oliver \person{Kurth}, starting in 1999. His aim was to create a small \mta\ which is especially focused on computers with dial-up connections to the internet. \masqmail\ is easy configurable for situations which are rarely solveable with the common \MTA{}s.

30

31 \masqmail\ queues mail for destinations outside the local network if no connection to the internet is online. If the machine goes online, this mail is sent. Mail to local machines is sent immediately.

32

33 While the other \MTA{}s are more general purpose \MTA{}s, \masqmail\ aims on special situations only. Nevertheless can it handle ordinary mail transfers too.

34

35 \masqmail\ is released under the \GPL, which makes it \freesw. The latest stable version is 0.2.21 from November 2005.

36

37 The program's new homepage \citeweb{masqmail:homepage} provides further information about this \MTA.

38

39

40 \subsubsection*{Target field}

41

42 Its original author, Oliver \person{Kurth}, sees \masqmail\ so:

43 \begin{quote}

44 MasqMail is a mail server designed for hosts that do not have a permanent internet connection eg. a home network or a single host at home. It has special support for connections to different ISPs. It replaces sendmail or other MTAs such as qmail or exim.

45 \end{quote}

46

47 \masqmail\ is inteded to cover a specific niche: non-permanent internet connection and different \NAME{ISP}s.

48

49 Although it can basically replace other \MTA{}s, it is not generally aimed to do so. The package description of \debian\citeweb{packages.debian:masqmail} states this more clearly by changing the last sentence to:

50 \begin{quote}

51 In these cases, MasqMail is a slim replacement for full-blown MTAs such as sendmail, exim, qmail or postfix.

52 \end{quote}

53 \masqmail\ is a good replacement ``in these cases'', but not generally, since is lacks features essential for running on mail servers. It is primarily not secure enough for being accessable from untrusted locations.

54

55 The program is best used in home networks, which are non-permanently connected to the internet. \masqmail\ sends mail to local destinations, like users on the same machine and on other machines in the local net, immediately. Email to recipients outside the local net are queued when offline and sent when a online connection gets established.

56

57 Further more does \masqmail\ respect online connections through different \NAME{ISP}s; a common thing for dial-up connections. In particular can different sender addresses be set, dependent on the \NAME{ISP} that is used. This prevents mail to be likely classified as spam.

58

59

60

61 \subsubsection*{Typical usage}

62 This section describes situations that make senseful use of \masqmail.

63

64 A home network consisting of some workstations without a server. The network is connected to the internet by dial-up or broadband. Going online is initiated by computers inside the local net. \NAME{IP} addresses change at least once every day.

65

66 Every workstation would be equiped with \masqmail. Mail transfer within the same machine or within the local net works straight forward. Outgoing mail to the internet is sent, to the concerning \NAME{ISP} for relaying, whenever the router goes online. Receiving of mail from outside needs to be done by a mail fetch program, like the \masqmail\ internal \NAME{POP3} client or \name{fetchmail} for example. The configuration for \masqmail\ would be the same on every computer, except the hostname.

67

68 For the same network but having a server, one could have \masqmail\ running on the server and using simple forwarders (see \ref{subsec:relay-only}) to the server on the workstations. This setup does only support mail transfer to the server, but not back to a workstation; also sending mail to another user on the same workstation is not possible.

69

70 A better setup is to run \masqmail\ on every machine %FIXME

71

72

73 \subsubsection{Online detection and routes}

74 \label{sec:masqmail-routes}

75

76 ---

77

78 As \masqmail\ is focused on non-permanent Internet connections, online state can be queried by three methods: reading from a file, reading the output of a command, or by asking an \name{mserver}. Each method may return a string indicating one of the available routes being online, or returning nothing to indicate offline state.

79

80 Delivery to recipients on the local host or in local nets is done at once; delivery to recipients on the Internet is only done when being online, and queued otherwise. Each online route may have a different mail server to which mail is relayed. Return address headers are modified appropriate if wished.

81

82 ---

83

84 \masqmail\ focuses on non-permanent online connections, thus a concept of online routes is used. One may configure any number of routes to send mail. Each route can have criteria, like matching \texttt{From:} or \texttt{To:} headers, to determine if some message is allowed to be sent over it. Mail to destinations outside the local network gets queued until an online connections is available.

85

86

87

88

89

90 \subsubsection*{\masqmail's main goal}

91

92 \masqmail\ does have similar requirements, by being a \sendmail\ replacement, which is a basic goal of the project. The main difference is that \masqmail\ is intended to be used on workstations and in small networks, but \sendmail, \qmail, and \postfix\ are designed to run on large mail servers to handle masses of email. The author of \masqmail, \person{Kurth}, in contrast, warns on the old project's website \citeweb{masqmail:homepage2} about using it to accept connections from the Internet, because of the risk to be an open relay:

93 \begin{quote}

94 MasqMail is not designed to run on a host with a permanent internet connection. It does not have the ability to check for spam mail and it will relay everything from everywhere to everywhere. Use another mail server such as exim for permanent connections.

95 \end{quote}

96 Even if some relay control will be added, ``is not designed to'' is a clear indicator for being careful. Issues like high memory consumption, low performance, and denial-of-service attacks---things not regarded by design---may cause serious problems.

97

98 Here shows a misfit off: On the one hand does \masqmail\ want to be a \sendmail\ replacement. But on the other hand, is it not designed to be used like \sendmail. If \masqmail\ is inteded to replace other \MTA{}s, then one may replace another one with it. Hence it must be secure enough. It either needs the security features or must drop the unsecure funtionality. The second option, however, leads to being \emph{no} replacement for other \MTA{}s. It is a valid decision to not be a replacement for \sendmail\ or thelike, but this is a design decision---the change of a primary goal.

99

100 If \masqmail\ should be an \MTA\ to replace others, a switch to a better suited architecture that provides good security and extendability by design, seems required. But if \masqmail\ is wanted to cover some special jobs, not to replace common \MTA{}s, then its architecture depends on the special requirements of the specific job; \MTA\ architectures, like discussed by \person{Hafiz}, may be inadequate.

101

102

103 \subsubsection*{Full featured or stripped down}

104

105 What future is to choose for \masqmail---one to be a full featured \MTA, or one to be a stipped down \MTA\ for special jobs?

106

107 The critical point to discuss upon is surely the listening on a port to accepte messages from outside via \NAME{SMTP} (herafter also refered to as the \NAME{SMTP}-in channel). This feature is required for an \MTA\ to be a \name{smart host}, to relay mail. But running as deamon and listening on a port requires much more security effort, because the program is put in direct contact with attackers and other bad guys.

108

109 \MTA{}s without \SMTP-in channels can not receive mail from arbitrary outside hosts. They are only invoked by local users. This lowers the security need a lot---however, security is a general goal and still required, but on a lower level. Unfortunately, as they do not receive mail anymore (except by local submission), they are just better \name{forwarders} that are able to send mail directly to the destination.

110

111 This is not what \masqmail\ was intended to be. Programs that cover this purpose are available; one is \name{msmtp}.

112

113 \masqmail\ shall be a complete \mta. It shall be able to replace ones like \sendmail.

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116

117

118

119

120

121

122 \subsubsection*{What makes it special}

123

124 As main advantage, \masqmail\ makes it easy to set up an \MTA\ on workstations or notebooks without the need to do complex configuration or to be an mail server expert.

125

126 Workstations use %FIXME

127

128 \textbf{Alternatives?}

129 % http://anfi.homeunix.org/sendmail/dialup10.html

130

131

132

133 << explain why masqmail is old and why it is interesting/important however! >> %FIXME

134

135 << why is it worth to revive masqmail? >>

136

137

138

139 \section{Problems to solve}

140

141 << what problems has masqmail? >> %FIXME

142

143 << what's the intention of this document? >> %FIXME

144

145 << why is it worth the effort? >> %FIXME

146

147

148 \section{What is not covered here}

149

150 << limit against stuff not covered here >>

151

152

153 \section{Further reading}

154

155

156 << specify the really important external documents here >> %FIXME

157

158 << write about the bundled CD, and tell what's included >> %FIXME

159

160 \NAME{RFC}s, other books, source code, websites

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163