I've seen this issue creeping up more and more lately and thought I'd post the fix, while we look into the 'why's'.
When trying to open RMS protected content via Outlook you may receive the error:
"Manifest does not match the executable, recreate the manifest by rebuilding the application."
This error happens because the Outlook shortcut is pointing to a UNC path to the local machine, instead of to the actual file path location to the executable. Just point the shortcut to the actual executable, and it should resolve the issue.
I don't know why this happens to the shortcut, but I hope this post helps.