I use Dreamweaver to design email templates for a newsletter in HTML.
Is there a way I can import the HTML code from this template directly into an Outlook message so I can sent it (as an example) to my clients?
You can inject HTML code into the message body via the Insert as Text option;
Insert-> (Attach) File-> select the created htm-file-> press the down arrow on the Insert button-> Insert as Text
Inject HTML directly into the message body.
This option no longer exists in Outlook 2016 new File Attach dialog. However, you can still bring back the classic dialog with the “Insert as Text” option as instructed in; Classic Attach File button and Insert as Text option in Outlook 2016.