For an official letter it can't do any harm to use a dedicated class which will do the general formatting. One of those classes is scrlttr2 from the »KOMA-Script« bundle. Although this class is very flexible (and thus quite complex), you can get quick and good results with basic settings like in this approach.
\documentclass[
fontsize=11pt,
paper=a4,
parskip=half,
enlargefirstpage=on, % More space on first page
fromalign=right, % PLacement of name in letter head
fromphone=on, % Turn on phone number of sender
fromrule=aftername, % Rule after sender name in letter head
addrfield=on, % Adress field for envelope with window
backaddress=on, % Sender address in this window
subject=beforeopening, % Placement of subject
locfield=narrow, % Additional field for sender
foldmarks=on, % Print foldmarks
]{scrlttr2}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage{blindtext}
\setkomafont{fromname}{\sffamily \LARGE}
\setkomafont{fromaddress}{\sffamily}%% statt \small
\setkomafont{pagenumber}{\sffamily}
\setkomafont{subject}{\bfseries}
\setkomafont{backaddress}{\mdseries}
\LoadLetterOption{DIN}
\setkomavar{fromname}{From Name}
\setkomavar{fromaddress}{From Street\\00000 From City}
\setkomavar{fromphone}{+49 0000 0\,00\,00\,00}
\setkomavar{fromemail}{from.name@mail.com}
\setkomavar{backaddressseparator}{\enspace\textperiodcentered\enspace}
\setkomavar{signature}{(From Name)}
\setkomavar{place}{From City}
\setkomavar{date}{\today}
\setkomavar{enclseparator}{: }
\begin{document}
\begin{letter}{To Name\\To Street\\00000 To Place}
\setkomavar{subject}{Subject}
\opening{Ladies and Gentlemen,}
\blindtext
\closing{Sincerely,}
\end{letter}
\end{document}
For details about the many options for customization please refer to the »KOMA-Script« user guide. You may also want to take a look at »newlfm«.

scrlttr2? You can set foldermarks, footer etc. Seetexdoc KOMA-Script(with examples!). – Mensch Sep 18 '13 at 08:13