docs/diploma

annotate thesis/tex/1-Candidates.tex @ 63:fbf5165a390f

added questions I asked on debianforum.de
author meillo@marmaro.de
date Sun, 19 Oct 2008 17:58:41 +0200
parents c90f75d3b7ad
children 997870769e54
rev   line source
meillo@31 1 \chapter{\unix\ \MTA{}s}
meillo@27 2
meillo@44 3 This chapter introduces a group of \mta{}s.
meillo@44 4 These will be presented to the reader in a short overview and with the most important facts.
meillo@44 5 The next chapter will show a comparison of the candidates in several disciplines.
meillo@27 6
meillo@27 7
meillo@28 8 \section{Types of \MTA{}s}
meillo@44 9 ``Mail transfer agent'' is a term covering a variety of programs.
meillo@44 10 One thing is common to them: they transport email from one \emph{thing} to another.
meillo@44 11 These \emph{things} can be hosts, meaning independent machines, or protocols like \NAME{SMTP} and \NAME{UUCP}, between which mail is transfered.\footnote{\sendmail{}'s initial purpose was moving mail between \NAME{UUCP}, \name{Berknet} and \NAME{SMTP}.}
meillo@27 12
meillo@44 13 Beside this common property, \MTA{}s can be very different.
meillo@44 14 Some of them have \NAME{POP3} and/or \NAME{IMAP} servers included.
meillo@44 15 Some can fetch mails through these protocols.
meillo@44 16 Others have have every feature you can think of.
meillo@44 17 And maybe there are some that do nothing else, but transporting email.
meillo@28 18
meillo@31 19
meillo@28 20 \section{The ones not regarded here}
meillo@44 21 The candidates for the competition in the next chapter are a subset of the \MTA{}s available.
meillo@44 22 Comparision between totally different programs (apart of one function) makes not much sense.
meillo@44 23 One would not use a program for a job it is not suited for.
meillo@44 24 Therefor \mta{}s that are rarely similar to \masqmail\ are not regarded.
meillo@28 25
meillo@44 26 The first group of programs to sort out are the so called \name{groupware} programs.
meillo@44 27 These provide a whole lot of functions, including mail transfer, file storage, calendars, resource management, instant messaging and more.
meillo@40 28 Examples for this kind of programs are: \name{Lotus Notes}, \name{Microsoft Exchange}, \name{OpenGroupware.org} and \name{eGroupWare}.
meillo@28 29
meillo@40 30 The second group are the \name{relay-only} \MTA{}s.
meillo@44 31 They transfer mail only to defined \name{smart hosts}\index{smart host}\footnote{\MTA{}s that receives email and route it to the actual destination}.
meillo@44 32 Most \MTA{}s can be configured to act as such a forwarder.
meillo@44 33 But this is normally an additional functionality.
meillo@28 34 Examples for that group are: \name{nullmailer}, \name{ssmtp} and \name{esmtp}.
meillo@28 35
meillo@44 36 Third, only \emph{sendmail-compatible} \MTA{}s will be regarded in the competition.
meillo@44 37 Hence all \MTA{}s not having a \emph{sendmail-compatible} interface or not offering it as a compatibility addon, will not be covered here.
meillo@44 38 The reason is the heavy reliance of \unix\ systems on the existance of a programs called \path{sendmail}.
meillo@44 39 This has historical reasons. See section \ref{sec:sendmail} for further information.
meillo@44 40
meillo@44 41 Further more, only programs with source code available are regarded. %FIXME: why
meillo@27 42
meillo@27 43
meillo@26 44 \section{The competitors}
meillo@28 45 The programs remaining are \emph{sendmail-compatible} ``smart'' \MTA{}s that do not offer masses of features unrelated to mail transport.
meillo@26 46
meillo@44 47 For the comparision, five programs of this group are taken.
meillo@44 48 These are: \sendmail, \name{qmail}, \name{postfix}, \name{exim} and \masqmail.
meillo@44 49 The four alternatives to \masqmail\ are the most important representatives of the regarded group.
meillo@44 50 %TODO: what about having one program as ``outsider'' ...?
meillo@44 51
meillo@44 52 Other, but not covered, group members are: %FIXME: are these all MTAs of that group? why these and not others?
meillo@58 53 %TODO: what about `courier-mta'?
meillo@27 54
meillo@57 55 % http://www.yolinux.com/TUTORIALS/LinuxTutorialMailMTA.html
meillo@57 56 % http://homepages.tesco.net/~J.deBoynePollard/Reviews/UnixMTSes/
meillo@57 57
meillo@28 58 Here follows a small introduction to each of the five.
meillo@27 59
meillo@28 60 \subsection{\sendmail}
meillo@60 61 \sendmail\ is the most popular \mta.
meillo@60 62 Since it was one of the first \MTA{}s and was shipped by many vendors of \unix\ systems.
meillo@60 63
meillo@60 64 The program was written by Eric Allman as the successor of his program \name{delivermail}.
meillo@60 65 \sendmail\ was first released with \NAME{BSD} 4.1c in 1983.
meillo@60 66 Allman was not the only one working on the program.
meillo@60 67 Other people developed own versions of it and a variety of flavors came up, especially in the late eighties when Allman was inactive.
meillo@60 68
meillo@60 69 \sendmail\ is focused on transfering mails between different protocols and networks, this lead to a very flexible (though complex) configuration.
meillo@60 70
meillo@60 71 The latest version is 8.14.3 from May 2008.
meillo@60 72 Further development will go into the project \name{MeTA1} which succeeds \sendmail.
meillo@60 73
meillo@60 74 More information can be found on the \sendmail\ homepage \citeweb{sendmail:homepage} and on \citeweb{wikipedia:sendmail} and \citeweb{jdebp}.
meillo@60 75 %FIXME: license
meillo@60 76
meillo@27 77
meillo@28 78 \subsection{\name{qmail}}
meillo@60 79 \name{qmail} is seen by its community as ``a modern SMTP server which makes sendmail obsolete''.
meillo@60 80 It was written by Daniel~J.\ Bernstein starting in 1995.
meillo@60 81 His primary goal was to create a secure \MTA\ to replace the popular, but vulnerable, \sendmail.
meillo@60 82
meillo@60 83 \name{qmail} first introduced may innovative concepts in \mta\ design and is generally seen as the first security-aware \MTA\ developed.
meillo@60 84
meillo@60 85 Since November 2007, \name{qmail} is released in the \name{public domain} which makes it \freesw.
meillo@60 86 The latest release is 1.03 from July 1998.
meillo@60 87
meillo@60 88 The programs homepages are \citeweb{qmail:homepage1} and \citeweb{qmail:homepage2}. Further information about \name{qmail} is available on \citeweb{lifewithqmail}, \citeweb{wikipedia:qmail} and \citeweb{jdebp}.
meillo@60 89
meillo@27 90
meillo@28 91 \subsection{\name{postfix}}
meillo@31 92 %TODO: author, date of first release, basic intention of program, ...
meillo@31 93 %TODO: references to various descriptions
meillo@27 94
meillo@28 95 \subsection{\name{exim}}
meillo@31 96 %TODO: author, date of first release, basic intention of program, ...
meillo@31 97 %TODO: references to various descriptions
meillo@28 98
meillo@28 99 \subsection{\masqmail}
meillo@44 100 The \masqmail\ program was written by Oliver Kurth, starting in 1999.
meillo@44 101 His aim was to create a \mta\ which is especially focused on computers with dial-up connections to the internet.
meillo@44 102 \masqmail\ handles situations which are rarely solveable with the common \MTA{}s.
meillo@31 103 %TODO: references to various descriptions
meillo@27 104
meillo@27 105
meillo@58 106 % briefly discuss the border between small MTAs (sendmail, masqmail) and state-of-the-art mailservers (postfix) and groupware (notes, exchange): give usecases.