Lengthen the horizontal area for signature block in a letter

letters

I have a generic rec letter template which I update as needed. It's great, except that the long name of the sub-department I work for wraps in my signature block and I don't want it to. Specifically, my signature block renders like this:

My Name
My Title
The Pretty Long Name of the 
Sub-Department That I Work For 
My University

While I'd prefer:

My Name
My Title
The Pretty Long Name of the Sub-Department That I Work For 
My University

I have tried moving the whole signature block to the left with \longindentation=15em, but it doesn't seem to have actually widened the block (just translated it).

Any help appreciated!

Below is the totality of my source:

\documentclass{letter}
\usepackage{hyperref}
\usepackage[margin=1in]{geometry}
\setlength{\parindent}{4em} % indentation of first line of paragraphs


\signature{My Name \\ My Title \\ The Pretty Long Name of the Sub-Department That I Work For \\ My University}
\address{My Name \\ My Office Address \\ My University}

\longindentation=15em % move the signature block a bit to the left so it's not starting at the center

\begin{document}

\begin{letter}{Recipient Department \\ Recipient Organization or University}

\opening{\noindent To whom it may concern:} % \noindent leaves this paragraph unindented

This is my letter which almost always consists of three paragraphs of text.

Here's the middle paragraph.

Here's the concluding paragraph.

\vspace{2em}
\closing{Sincerely,}

\end{letter}
\end{document}

Best Answer

letter class places the signature in

 \hspace*{\longindentation}\fi
  \parbox{\indentedwidth}

so you can increase the length \indentedwidth but if you increase it too much you will need to reduce \longindentation so it stays on the page.