It's working for me here on LInux. I've never tried a direct paste before, since I'd usually want to crop the image or obfuscate personal info, so I almost always go through an image editor such as Gimp. But the bit of your description that surprises me is the "cntrl-shift printscreen". As far as I know, on Windows ''prtsc'' on its own captures the screen, and ''alt+prtsc'' captures just the active window. (Though personally I prefer to use a dedicated screenshot program that lets me select a window or desktop or a specific rectangular area.) Can I suggest you do your funny keystroke and try pasting it into Paint, just to check that it does actually do a screen capture. My test confirms that Thunderbird (I'm running v47 here) is capable of accepting pasted image data, so it would be good to be sure you do have some data on your clipboard to work with.