The broken image in your e-mail signature is the result of moved image resources. To fix, replace the old image path with the new one, like so:
1) Open a plain text editor. On a Windows machine you might use Notepad, on a Mac you might choose TextEdit.
2) From the File menu, choose Open... and locate your signature file (possibly named signature.html).
3) Replace the OLD IMAGE PATH
with the NEW IMAGE PATH
4) Save the file.
That should correct the problem.
Find complete e-mail signature instructions at www.pdx.edu/university-communications/download-e-mail-signature.