I right click an image, select copy image. Open a compose window and paste. The image appears

If I open windows paint and paste there I get an error message about the image not being suitable for paint. (because it is a remote image on a web site)

"I right click an image, select copy image. Open a compose window and paste. The image appears"

I'm glad that works for you, but it doesn't work for me. I just tried with a new compose window, no joy.

When I view the message source I see the hundreds of lines of MIME code. When I copy this code into an online decoder, I get the image. I can then copy the image and paste it into Xnview and worth with it from there. But I'm not able to right-click copy and paste from the image displayed in Thunderbird.

I'm also not offered a Save option at the bottom, i.e. the image isn't recognized as an attachment.