When you put your cursor over the image of the video and right-click, you are actually saving only an image. The email also contain the video file attachment to save to your computer. Look for the attachment section of the email, right-click over the attachment icon, and select Save As.  Now go to where you saved the video and open the video. 

**Alternate method, you can send the video to your wireless number, forward the video to your email address, and right-click the video attachment and save as.