When I replied to a fully MIME-encoded message with embedded images, that's one of them --_008_6F451195E3BF43A994B73D0079C6D388windreamcom_ Content-Type: image/png; name="imagec2cad0.PNG" Content-Description: imagec2cad0.PNG Content-Disposition: inline; filename="imagec2cad0.PNG"; size=1075; creation-date="Wed, 25 Nov 2015 17:05:22 GMT"; modification-date="Wed, 25 Nov 2015 17:05:22 GMT" Content-ID: <imagec2cad0.PNG@1c5b46cf.41b03add> Content-Transfer-Encoding: base64 they have been replaced in my reply by an image from my desktop. The reply was totally reformatted by Thunderbird (V 38.4.0), a link (path, filename) to my image isn't part of the body. Instead I only find the URL that was combined with the received image <http://www...com>, when viewing the message as plain text. When viewing as Original HTML then Thunderbird shows the replaced image. I'm using Thunderbird for many years but have never seen such an error. And it is not easy to reproduce.