View RAW message source of an email in Outlook 2013

Headers

1. Open the particular email in a new window by double-clicking on the message in the message list. (This is important, it's not enough to be just looking at the message in what Outlook calls the 'reading pane'.)
2. Follow the menu File | Info | Properties
3. Look for a text area labelled Internet headers
4. Here are the headers. Select and copy the text to a text editor.

Content

1. Open message in a new window
2. On the Message ribbon, select Action | Other Actions | View Source.

1. Open message in new window
2. On the Message tab select Actions dropdown (next to Move button)
3. Select Other Actions → Source