The only problem with this is Blumenthal was not a government employee. He could have marked the email 'super extra top secret' and it would have been meaningless.
The moment that Hillary forwarded this information made it Classified. She would have been the person responsible to label same. Sid B. worked for the Clinton Foundation and thus comingling information with the SOS and the Foundation. This is more than unethical. This is clearly criminal and Treasonous.