Saving .eml file with X-Unsent: 1 is not working f

问题:

The .eml file created with below contents works appropriately in Outlook, however, when you open it with Lotus Notes 8.5 - it's not shown as draft email. It comes-up as a normal email, like it is in Inbox. If I try to Forward the email, then the image section is shown with a RED X.

I need to create an draft email which can be opened both in Outlook and Lotus Notes with HTML body. Any suggestions on how to create an .eml file for Lotus Notes?

I am using C#, to generate the .eml file.

        X-Sender: [e-mail]
        X-Receiver: [e-mail]
        X-Unsent: 1
        MIME-Version: 1.0
        From: [e-mail]
        To: [e-mail]
        Date: 23 Jan 2017 11:42:31 +1100
        Subject: Test subject
        Content-Type: text/html; charset=us-ascii
        Content-Transfer-Encoding: quoted-printable

        <br /><strong>Test body</strong><img src=3D'http://www.w3schools.=
        com/tags/smiley.gif' width=3D'42' height=3D'42'>

Appreciate any guidance on this part.