Have you ever received an email in Gmail with an image that expanded off the right side of the screen requiring you to scroll to the right to read it?
Not only does this make it difficult to read the email and/or compose a response, but all future emails within the Gmail Conversation have the same issue.
While there is no way to prevent this from occurring, there is a way to fix it after it occurs.
Just forward the email to yourself without the picture or with a resized picture.