How can I forward email as a readable attachment?
Solution 1:
If you find the message in Library->Mail copy the .emlx file into the email then you will be able to see it nicely in mail (worked for me).
Unfortunately, the challenge here would be to find the message that you want to send (since the file categories seem arbitrary, at least to me).
Solution 2:
The only way I have found this to work is to copy (drag) the attachment to the Desktop and rename it from "Attachment" to "Attachment.eml" and drag it back in again.
I've never had people tell me they cannot open the "Attachment.eml".