I'd always do resizing, rotation, etc, in a specialized graphics program. Irfanview is my favourite in Windows. http://www.irfanview.com/ You can position and re-size an image in Thunderbird. Select the image and go to Format in the composition window's menu, or double-click the image itself. Then you'll see a Properties editor. But this Properties editor doesn't offer rotation. For that you will need to use a program, and ideally one that doesn't silently obey the exif data that tells it which way up your picture goes; you need to rotate it yourself to be sure the image will appear to an email correspondent as you want it to appear. Exif data is added to a picture by the camera, tablet or phone that took the picture. This data often includes info about orientation and some viewer programs will use this to automatically rotate the picture when showing it. But Thunderbird, and many other email clients, doesn't do this, so we have to do it for them.