\RequirePackage{filecontents}
\begin{filecontents*}{DIN5008A-deprecated.lco}
%
% This is file `DIN5008A-deprecated.lco'.
% Copyright (c) 2015 Markus Kohm [komascript at gmx info]
% 
% This file may be distributed and/or modified under the conditions of
% the LaTeX Project Public License, version 1.3c of the license.
% The latest version of this license is in
%   http://www.latex-project.org/lppl.txt
% and version 1.3c or later is part of all distributions of LaTeX
% version 2005/12/01 or later.
%
% This work has the LPPL maintenance status "maintained".
%
% The Current Maintainer and author of this work is Markus Kohm.
%
% For more information see: <https://komascript.de/DIN5008A.lco>.
%
\immediate\write17{^^J%
+----------------------------------------------------------------------^^J%
| WARNING (`DIN5008A-deprecated.lco'):^^J%
+----------------------------------------------------------------------^^J%
| THIS FILE IS DEPRECATED!^^J%
| DON'T INSTALL IT!^^J%
| DON'T USE IT!^^J%
| Please, use `DIN5008A.lco' or `DIN5008B.lco' that come with^^J%
| KOMA-Script since version 3.27.^^J%
+----------------------------------------------------------------------^^J%
}
\ProvidesFile{DIN5008A-deprecated.lco}[2015/02/16 v0.1 deprecated letter-class-option]
\LoadLetterOption{DINmtext}
\KOMAoptions{fromalign=locationleft,addrfield=topaligned,refline=narrow}
\@setplength{firstheadhpos}{25mm}
\@setplength{firstheadwidth}{100mm}
\@setplength{specialmailindent}{5mm}
\@setplength{specialmailrightindent}{0pt}
\@setplength{toaddrindent}{5mm}
\@setplength{lochpos}{-125mm}
\@setplength{locvpos}{32mm}
\@setplength{locwidth}{75mm}
\@setplength{refvpos}{\dimexpr\useplength{tfoldmarkvpos}-32pt}
\@setplength{refaftervskip}{8.46mm}
\@newplength{specialmailheight}
\@setplength{specialmailheight}{12.7mm}
\newcommand*{\textareabydin}{%
  \areaset{165mm}{233mm}%
  \setlength{\oddsidemargin}{\dimexpr 25mm-1in}%
  \setlength{\evensidemargin}{\dimexpr 20mm-1in}%
}
\renewcommand{\backaddr@format}[1]{\hspace*{\useplength{toaddrindent}}%
  \parbox[t][\useplength{backaddrheight}][t]%
         {\dimexpr\useplength{toaddrwidth}-\useplength{toaddrindent}}%
         {\strut\ignorespaces #1\unskip\strut}%
}
\renewcommand{\specialmail@format}[1]{%
  \parbox[t][\useplength{specialmailheight}][t]%
         {\dimexpr\useplength{toaddrwidth}-\useplength{specialmailindent}-\useplength{specialmailrightindent}}%
         {\strut\ignorespaces #1\unskip\strut}%
}
\setkomafont{specialmail}{\sffamily\fontsize{10pt}{12pt}\selectfont}
\setkomafont{backaddress}{\sffamily\fontsize{8pt}{10pt}\selectfont}
\setkomafont{addressee}{\sffamily\fontsize{10pt}{12pt}\selectfont}
\setkomafont{fromname}{\sffamily\fontsize{10pt}{12pt}\selectfont}
\setkomafont{fromaddress}{\sffamily\fontsize{10pt}{12pt}\selectfont}
\setkomafont{refvalue}{\sffamily\fontsize{10pt}{12pt}\selectfont}
\let\raggedsignature\raggedright
\end{filecontents*}

\documentclass[fontsize=12pt,fromphone,fromfax,fromemail]{scrartcl}
\usepackage[utf8]{inputenc}
\usepackage[ngerman]{babel}
\usepackage{lmodern}
\usepackage{scrletter}
% IMPORTANT NOTE:
% With KOMA-Script 3.27 or newer it is recommended to use:
%\LoadLetterOption{DIN5008A}
% instead of:
\LoadLetterOption{DIN5008A-deprecated}
\textareabydin
% END-NOTE

\setkomavar{backaddress}{Rücksendeadresse}
\setkomavar{yourref}{abc-01}
\setkomavar{yourmail}{2013-04-23}
\setkomavar{myref}{mihh-00}
\setkomavar{fromname}{Max Muster}
\setkomavar{fromaddress}{Musterhaus 1\\99999 Musterstadt}
\setkomavar{fromphone}{040~1234-5678}
\setkomavar{fromfax}{040~1234-7890}
\setkomavar{fromemail}{max.muster@invalid.invalid}
\setkomavar{date}{2013-04-30}

\usepackage{mwe}

\begin{document}

\setkomavar{specialmail}{VZ3\\VZ2\\VZ1}

\begin{letter}{AZ1\\AZ2\\AZ3\\AZ4\\AZ5\\AZ6}
\opening{Sehr geehrte Damen und Herren}
\Blindtext
\closing{Mit freundlichen Grüßen}
  
\end{letter}

\end{document}

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