Hi Spudda,
I can fully understand your situation.
Generally, we can use RTF when sending messages within an organization that uses Microsoft Exchange. However, it is recommended we use the HTML format so that we can make sure that what we send is what the recipient will see.
RTF supports text formatting, including bullets, alignment, and linked objects. Outlook automatically converts RTF formatted messages to HTML by default when we send them to an Internet recipient, so that the message formatting is maintained and attachments are received.
For more detailed information, you can refer to this link:
Change the message format to HTML, Rich Text, or plain text
To narrow down this issue, I would like to confirm the following information:
1. Do you mean the embedded images show up as the picture below when they disappeared?
2. You mentioned "when we change it to Rich Text the images appear and come across to the Archive". I would like to confirm whether the issue persists or not in OWA after changing to Rich Text format via Outlook.
3. If the pictures are not taken by snipping tools, will the issue exist?
Thanks,
Chris Ni