Manjunatha suggested this tip:

You can copy some text (might be from Excel, Word, Powerpoint, or even some old mail) into new mail.

1. Copy the selection
2. Move to the Inbox
3. Press Shift+Ins

Note: this works not only for mail but for any Outlook item - select the folder and press Shift+Ins to create a new item of the folder type using the contents of the clipboard. You can also use paste (Ctrl+V) or even select some text and drag it to a folder to create a new item. You can use the shortcut keys almost anywhere within the Outlook message list or preview window, or select a folder in the navigation pane, folder list, or Outlook bar.