\documentclass{scrlttr2}
\usepackage[ngerman]{babel}
\usepackage[latin1]{inputenc}
\usepackage{lipsum}
\setkomavar{fromname}{Hans Froschkönig}
\setkomavar{fromaddress}{Unter den Weiden 10 \\ 12345 Quakstadt}
\setkomavar{fromemail}{hans@quakstadt-online.de}
\KOMAoptions{backaddress=false,foldmarks=off}
\addtolength{\headsep}{2cm}
\addtolength{\textheight}{-2cm}

\firsthead{\usekomafont{pagehead}%
	\strut\parbox[t]{\useplength{firstheadwidth}}{%
	\hspace*{\fill}%
	\large\scshape\usekomavar{fromname}}\\
	\rule{\useplength{firstheadwidth}}{.4pt}%
}

\nexthead{\usekomafont{pagehead}%
	\hspace*{\oddsidemargin}\hspace{-1in}%
		\hspace{\useplength{toaddrhpos}}%
			\makebox[\textwidth][l]{%
			\parbox[b]{\useplength{firstheadwidth}}{%
	{\usekomafont{pagenumber}\pagename~\thepage}%
	\hspace*{\fill}%
	\large\scshape\usekomavar{fromname}\\
	\rule{\useplength{firstheadwidth}}{.4pt}\\
}}}

\newcommand{\myfoot}{
        \begin{tabular}{l}
                \usekomavar{fromname}
        \end{tabular}%
        \hfill
        \begin{tabular}{l}
                \usekomavar{fromaddress}\\
        \end{tabular}%
        \hfill
        \begin{tabular}{l}
                \llap{\usekomavar*{fromphone}~}\usekomavar{fromphone}
                \ifkomavarempty{fromfax}{}{\\%
                        \llap{\usekomavar*{fromfax}~}\usekomavar{fromfax}}
                \ifkomavarempty{fromemail}{}{\\%
                        \llap{\usekomavar*{fromemail}~}\usekomavar
{fromemail}}
                \ifkomavarempty{fromurl}{}{\\%
                        \llap{\usekomavar*{fromurl}~}\usekomavar{fromurl}}
        \end{tabular}}

\firstfoot{\scriptsize
	\usekomafont{pagehead}%
	\strut\parbox[t]{\useplength{firstfootwidth}}{%
	\rule{\useplength{firstfootwidth}}{.4pt}\\[1em]%
	\myfoot}}
	
\nextfoot{\scriptsize
	\usekomafont{pagehead}%
	\hspace*{-\oddsidemargin}\hspace{-1in}%
		\hspace{\useplength{toaddrhpos}}%
			\makebox[\textwidth][l]{%
			\parbox[t]{\useplength{firstfootwidth}}{%
			~\\[-\dp\strutbox]%
	\rule{\useplength{firstfootwidth}}{.4pt}\\[1em]%
	\myfoot}}}
	
\pagestyle{headings}
\begin{document}
\begin{letter}{Ariane Nimmermehr \\ Quakstadt}
\opening{Liebe Ariane,}
  \lipsum
\closing{Mit bester Empfehlung}
\end{letter}
\end{document}