Mac Mail: "This message has no content"
Not a question but a workaround for those who need it
This has been a long-running issue Apple has failed or not bothered to fix.
SOLUTION: The message you want to view drag it to a new mailbox and then drag it back again. You should then be able to view the content.
For some reason, the content will only appear after you drag in back into the original mailbox.
No idea why this works, but it does and took me ages to figure this one out.
APPLE why not finally fix this?
MacBook Air