title: Terminal's "codesign" command trouble
body: <p>I've been trying to use the "codesign" command on Mail.app so that I can modify the info.plist using the "defaults write" command. It used to work, but after I re-installed Yosemite, I get this result when running the command:</p>
  
  <pre><code>/Applications/Mail.app: no identity found
  </code></pre>
  
  <p>I ran this command:</p>
  
  <pre><code>codesign -f -s /Applications/Mail.app
  </code></pre>
  
  <p>If anyone could tell me how I could properly run the codesign command on Mail.app so that I can modify the info.plist of Mail.app using the "defaults write" command, that would be nice! Thanks!</p>