\documentclass[11pt]{letter}
\usepackage{purduelh}
\begin{document}
%%% all the following customizable fields are optional.
\lhname{Joe Doe}% default: empty
\lhtitle{Job Title}% default: empty
% \lhphone{765-494-1901}% default: dept phone
% \lhfax{765-494-0548}% default: dept fax
\lhemail{jdoe@math.purdue.edu}% default: user@math.purdue.edu
\lhurl{http://www.math.purdue.edu/\~{}jdoe}% default: dept url

\begin{letter}{}
\colorlh  % without this, a black & white logo is produced.
\purduelh
\address{Test Address}
\opening{To whom this may concern,}

\medbreak\parindent=20pt

This is a test.

\signature{Jiu-Kang Yu}
\closing{Sincerely,}

\end{letter}

\end{document}