No, it's not yours, it's the sender's fault.
They probably drag&dropped image in their mail compose window and the worst part is that their email provider don't support such feature or they did it incorrectly.
Ask them to attach the image to the mail or if you can't do so you can still open the image using it's base64 encoding (the long series of alphabets and numbers). Copy the long text inside the quotes after
src and paste it into the browser's addressbar and hit enter, if done correctly you will see the image. But it's difficult to work with such long text so you better ask them to upload the image somewhere and share it with you.