Forwarding breaks embedded inline images?

[apjanke]

If I forward the "screenshot sample" email to myself at work, where we're running Exchange/Outlook, the embedded inline images break.

The breakage seems to happen as soon as I create the forward in Thunderbird:

What I've seen

Email Client	Behavior
Thunderbird 78.6 on macOS 10.14	Loses images as soon as it creates the forward
Outlook on Windows	Keeps the images, but loses the flexbox arrangement
Mac Mail.app on macOS 10.14	Keeps the images! They get real big when previewing the forward, but look fine again when I receive the mail in Thunderbird or Mail.app
GMail web client on Chrome on Mac	Images are kept, but resized and they lose the flexbox arrangement

[apjanke]

I looked at the raw email I received at work, and it indeed seems the embedded image parts are not included; just the file attachment.

Am I doing something wrong with the embedded images? Issue with Thunderbird?

[apjanke]

Related Thunderbird bug?

https://bugzilla.mozilla.org/show_bug.cgi?id=560210

[apjanke]

I think it's a Thunderbird issue. If I send the email first to my Exchange email at work, and then forward it from Mac Outlook to my home address, the images are retained. Though the flexbox styling that makes them line up correctly is lost.