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1 \chapter{Introduction}
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2
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3 \section{History of electronic mail}
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4 %TODO: have a quote from Bell Labs about email here
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5 %FIXME: add references to text
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6
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7 Electronic mail (short: \name{email}) is a basic concept in \unix. On \unix\ machines, a lot of information is distributed by \name{system mail}, which is email sent by the operating system. Beside that, email is the common communication system between humans working on computers.
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8
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9 The \unix\ operating system supports email since 1979 through the \name{mail user agent} (\NAME{MUA}) \path{/bin/mail}. For transporting mail in between two systems, the \NAME{UUCP} protocol (for ``\unix\ to \unix\ copy'') was invented.
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10 %FIXME: what about `uuxqt' and `rmail'
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11
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12 As generally known, the early development of \unix\ was not only made in the \name{Bell Labratories} of \NAME{AT\&T}. But also the \name{Univerity of California at Berkeley} worked on their version of a \unix\ operating system, called \NAME{UCB} \unix, or \name{Berkeley} \unix.
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13
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14 This lead to a second \NAME{MUA} from Berkeley: \name{Mail} (with a capital `M'). Also, no \NAME{UUCP} network was set up at Berkeley but an own creation called \name{BerkNet} was used.
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15 %FIXME: why? license issues? closed source?
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16 %TODO: what about `mailx'?
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17
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18 Further more there was a third network type: the \NAME{ARPAnet}, based on the \name{transmission control protocol} (\NAME{TCP}).
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19 %FIXME: where did it came from?
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20
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21 Each of the three network types could transfer email between different machines. The file transfer itself was made using \NAME{FTP}, but the higher layered logic of the transfer was different in each. For example was the addressing schema not the same: \NAME{UUCP} used a flat-style schema, while \NAME{ARPAnet} was hierachical.
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22
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23 Mail transport from one machine using one kind of network to a second machine using another kind was a problem. This showed up at Berkeley where some departments of the university had switched to \NAME{ARPAnet}, and some to \NAME{UUCP}, while the rest was \name{BerkNet}.
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24
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25 It was around 1982, when Eric Allman, then a student at Berkeley, wrote \name{delivermail}. Its purpose was to transform email from one network to another. \name{delivermail} like its successor, the more flexible \sendmail, intermediated between the different networks. They were able to transform email messages from any network to any other.
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26
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27 Todays email structure is basicly the same as then. The major difference is the uniformity of the underlying network, which is nearly always the \NAME{ARPAnet}-based \name{Internet}. Most other differences are organized as extensions to the old model of electronic mail.
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28
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29 More information about electronic mail and its history can be found at:
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30 %FIXME: add books and websites here
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31
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32
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33
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34 \section{Transporting mail}
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35 %TODO: include definitions from others here (cites)
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36 %TODO: when was the term ``mail transfer agent'' established?
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37 The basic job of a \name{mail transfer agent} (or \name{mail transport agent}, short \NAME{MTA}) is to transfer/transport \name{electronic mail} (short \name{email}) from one host to another.
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38
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39
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40
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41
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42 \section{\sendmail}
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43 \name{sendmail} is the de facto standard for \name{mail transfer agents}.
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44
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45 % FIXME: is that true?
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46 It was the first \NAME{MTA} and had no real alternative for a long time.
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47
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48 All other existing substitutes, which are mainly \name{postfix}, \name{exim}, \name{qmail} and the here regarded \name{masqmail}, mimic \name{sendmail}'s behavior. Especially, they all create a symbolic link named ``sendmail'' pointing to their own executable. This is because a lot of programs assume there is an executable called ``sendmail'' on every computer system.
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49
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50 Besides being the ``standard'', \name{sendmail} probably is the most scalable and powerful solution for transfering emails and definatly the most flexible one.
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51
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52
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53
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54 \section{(a look at Windows)}
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55
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