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author meillo@marmaro.de
date Sat, 10 Jan 2009 15:41:39 +0100 (2009-01-10)
parents fb9ba63f6957
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1 \chapter{About \name{mail transfer agent}s}
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3 % TODO: describe content of this chapter here
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6 \section{What is a \name{mail transfer agent}?}
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7 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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9 % TODO: include definitions from others here (cites)
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12 \section{History of \NAME{MTA}s}
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13 % FIXME: is that true?
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14 In the old days, the 70s, when Unix was created, computers were expensive. Universities and big firms normally had a single server with an amount of terminals connected to it. The computer filled a whole room somewhere in the cellar. People were operating at the terminals that were located in the offices and wired to the server. At that time, there was hardly no networking at all.
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16 During the following years, when computers became affordable and so more common (but still no personal computers at that time), connections between single computers were established. Inter-university connections were one of the first networks.
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18 Electronic mail is a basic concept in Unix. A lot of information gets distributed via system mail on Unix machines. System mail is electronic mail that stays on one machine. In nowadays this is primary notifications from system programs. But back then, there were frequently sent emails between users on the same machine.
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20 When computers were connected to each other and networks grew, the need appered to send electronic mail from one machine to another. E.g. Alice sitting on a terminal connected to server1 wants to send email to Bob sitting on a terminal connected to server2.
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22 Unix provided everything for that task, except a good tool to do the mail transport from server1 to server2.
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24 At that point the fathers of Unix at \name{Bell Labs} wrote the \NAME{UUCP} program and its compagnons. At about the same time in Berkeley a different solution for the same problem was developed: Eric Allman wrote \name{sendmail}.\footnote{To be exact: He wrote \name{delivermail} which he enhanced to \name{sendmail}.}
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27 \section{About \name{sendmail}}
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28 \name{sendmail} is the defacto-standard for \name{mail transfer agents}.
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30 % FIXME: is that true?
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31 It was the first \NAME{MTA} and had no real alternative for a long time.
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33 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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35 Besides being the ``standard'', \name{sendmail} probably is the most scalable and powerful solution for transfering emails and definatly the most flexible one.