\begin{tabular}[Hbt]{| l | c || c | c | c |}
	\hline
	Requirement           & Focus & S1 & S2 & S3 \\
	\hline \hline
	\RF7: encryption        & +++ & x  &    &   \\
	\RF6: authentication    & +++ & x  &    &   \\
	\RG1: security          & +++ &    & x  & x \\
	\RG2: reliability       & +++ &    &    & x \\
	\RF8: spam handling     & +++ & x  & x  & x \\
	\RG4: extendability     & +++ &    &    & x \\
	\hline
	\RG3: robustness        & ++  &    &    & x \\
	\hline
	\RF1: in/out channels   & +   & x  & x  & x \\
	\RF2: mail queueing     & +   &    &    & x \\
	\RG5: maintainability   & +   &    &    & x \\
	\hline
	\RF5: route selection   & 0   & x  &    &   \\
	\RF9: malware handling  & 0   & x  & x  & x \\
	\RF10: archiving        & 0   & x  &    & x \\
	\RG6: testability       & 0   &    &    & x \\
	\hline
	\RF3: header sanitizing & -   & x  &    &   \\
	\RF4: aliasing          & -   & x  &    &   \\
	\RG10: usability        & -   & x  &    &   \\
	\hline
	\RG8: availability      & -{}- & x &    &   \\
	\hline
	\RG7: performance       & -{}-{}- & x &  &  \\
	\RG9: portability       & -{}-{}- & x &  &  \\
	\hline \hline
	Score (Sum of `+')      & 23  & 9  & 7  & 17 \\
	\hline
\end{tabular}




