It's an old issue.
by R. Proffitt - 7/19/12 8:50 AM
In Reply to: Why do I get message that pictures can't be found? by kagemi
If you google that message you find it's been discussed to death. I didn't offer more than this because I'm unsure which exact email software and version you are using.
The most common workaround is not to forward but to create a new message and copy/paste the content.