You can insert text or HTML files in messages in Outlook (any version.) Use this to insert "boilerplate text" or HTML created in an HTML editor.
In Outlook 2016, you need to customize the Quick Access Toolbar or Ribbon to add the Insert File command to the ribbon - the default Attach File command on the Insert menu won't offer the opportunity to insert a file as text. The old Attach File command, which has the Insert as Text option is available in the customize dialog.
Tip: Make sure you choose the second Attach File command, the one that does not expand.
To Insert text or HTML files into a message:
- Click the Attach File icon in Outlook 2007, 2010, and 2013
- Select the file and expand the Insert button.
- Select Insert as text. If the file contains HTML tags, it will render in the message as HTML.
You can use VBA to insert HTML stationery or text files as the message body. See Create a New Message using an HTML File or Stationery for the code.