1.1 --- a/thesis/tex/3-MailTransferAgents.tex	Mon Dec 15 13:45:59 2008 +0100
     1.2 +++ b/thesis/tex/3-MailTransferAgents.tex	Mon Dec 15 16:59:01 2008 +0100
     1.3 @@ -71,7 +71,10 @@
     1.4  
     1.5  The programs chosen are: \sendmail, \exim, \qmail, and \postfix. They are the most important representatives of the regarded group. Although \MTA\ statistics are rare, differ, and good data is hard to collect, these programs tend to stay near the top.
     1.6  
     1.7 -Table \ref{tab:mta-market-share} shows the most used \MTA{}s determined by three different statistics. The first done Ken \person{Simpson} and Stas \person{Bekman} published by \name{O'ReillyNet} in 2007 \citeweb{oreillynet:mta-stats} , the second by \name{MailRadar.com} with unknown date \citeweb{mailradar:mta-stats} , and the third by Daniel~J.\ \person{Bernstein} (the author of \qmail) done in 2001 \citeweb{djb:mta-stats}.
     1.8 +
     1.9 +\subsection{Market share analysis}
    1.10 +
    1.11 +Table \ref{tab:mta-market-share} shows the most used \MTA{}s determined by three different statistics. The first was done by Daniel~J.\ \person{Bernstein} (the author of \qmail) in 2001 \citeweb{djb:mta-stats}. The second is by \person{Simpson} and \person{Bekman} in 2007 and was published by \name{O'ReillyNet} \citeweb{oreillynet:mta-stats}. And the third is from \name{MailRadar.com} with unknown date\footnote{The footer of the website shows ``Copyright 2007'' but more likely does this refer to the whole website.} \citeweb{mailradar:mta-stats}.
    1.12  
    1.13  \begin{table}
    1.14  	\begin{center}
    1.15 @@ -81,12 +84,18 @@
    1.16  	\label{tab:mta-market-share}
    1.17  \end{table}
    1.18  
    1.19 -All surveys show high market shares for the four \MTA{}s---\sendmail, \exim, \qmail, \postfix. Only the \name{Microsoft} mail servers and \name{IMail} have comparable large shares. Other \freesw\ \mta{}s are: \name{smail}, \name{zmailer}, \name{MMDF}, and \name{courier-mta}. They all are less important and rarely used.
    1.20 +All surveys show high market shares for the four \MTA{}s: \sendmail, \exim, \qmail, and \postfix. Only the \name{Microsoft} mail server software and \name{IMail} have comparable large shares. Other \freesw\ \mta{}s are: \name{smail}, \name{zmailer}, \name{MMDF}, and \name{courier-mta}. They all are less important and rarely used.
    1.21  
    1.22 -The three surveys base on different data. \person{Bernstein} took 1,000,000 randomly chosen \NAME{IP} addresses, containing 39,206 valid hosts; 958 of them accepted a connection. \name{MailRadar}'s data source is unspecified, as well as the time of data collection. The \name{O'Reilly} survey used only domains with companies behind them; in total it were 400,000 hosts.
    1.23 +The three surveys base on different data. \person{Bernstein} took 1,000,000 randomly chosen \NAME{IP} addresses, containing 39,206 valid hosts; 958 of them accepted \NAME{SMTP} connections. The \person{Simpson} and \person{Bekman} survey used only domains owned by companies; in total 400,000 hosts. \name{MailRadar} scanned 2,818,895 servers, leading to 59,209 accepted connections.
    1.24  
    1.25 -Remarkable are the 22 percent of ``mail security layers''\footnote{mail security layers are software guards between the network and the \mta\ that filter unwanted mail before it reaches the \MTA. This increases security by blocking attacks against the \MTA\ and by filtering malicious content. It also decreases the work load of the guarded \MTA.} in the \name{O'Reilly} survey. This large share may be a result of only regarding business mail servers. The problem concerning the survey is the deguise of the \mta\ working behind the security layer. It seems wrong to assume equal shares for the \MTA{}s behind the guards as for the unguarded \MTA{}s, because they will be more often used to guard weak \MTA{}s, as strong ones might not need them. This needs to be kept in mind when using the \name{O'Reilly} survey.
    1.26 +All surveys show \sendmail\ to be the most popular \MTA. \postfix, \qmail, and \exim\ are among the best seven in each. \exim\ has lightly smaller shares than the other two. The four together share more than half of the market according to \person{Bernstein} and the \name{MailRadar} statistics. \person{Simpson} and \person{Bekman} have their share to be somewhere between a third and the half. The reason for this uncertainty follows.
    1.27  
    1.28 +Remarkable are the 22 percent of ``mail security layers''\footnote{\name{mail security layers} are software guards between the network and the \mta\ that filter unwanted mail before it reaches the \MTA. This increases security by filtering malicious content and by blocking attacks against the \MTA. It also decreases the work load of the guarded \MTA.} in the \name{O'Reilly} survey. This large size of this share may be a result of only regarding business mail servers. The problem concerning the survey is the deguise of the \mta\ working behind the security layer. It seems wrong to assume equal shares for the \MTA{}s behind the guards as for the unguarded \MTA{}s, because they will be more often used to guard weak \MTA{}s, as strong ones do not need them so much. This needs to be kept in mind when using the \name{O'Reilly} survey.
    1.29 +
    1.30 +It seems quite sure that the \name{MailRadar} statistics were published after 2001, caused by the \sendmail\ and \postfix\ shares. But to decide whether before or after the one from \name{O'Reilly} would be just a guess.
    1.31 +
    1.32 +
    1.33 +\subsection{The four major Free Software MTAs}
    1.34  
    1.35  Now follows a small introduction to the five programs chosen for comparison, except \masqmail\ which already was introduced in chapter \ref{chap:introduction}. Longer introductions, including analysis and comparison, were written by Jonathan de \person{Boyne Pollard} \citeweb{jdebp}.
    1.36