The Tclkit DIN-Brief [http://wolf-dieter-busch.de/html/res/Heimatseite/download/dinbrief.kit] (available at [http://wolf-dieter-busch.de/html/Software/DINBrief.htm]) allows writing a well typeset TeX letter according to DIN 676 without the needs to hack some TeX markup. 

   * Numbered or bulleted lines are transformed to an appropriate TeX construction.
   * Tabs are transformed to an appropriate TeX construction.
   * Sub-subjects are marked with enclosing by "*" or "/" or "_" at line start, e.g. /New./
   * Including simple incremental search.

[http://wolf-dieter-busch.de/html/res/Heimatseite/img/sw/DIN-Brief.png]