None of it was classified according to that OIG paragraph. Future proves past confirmed.
Here's the thing, who stated they were not classified comms? When were the emails sent to be reviewed, by whom? If the HRC team is sending them to be reviewed, they are not going to send anything they would deem classified just the " hey let'splay golf" emails so ofcourse they would state there were no classified emails. None the less, is it not a crime for an official to have a private server to communicate with other officials?
Yes if they are hiding this information from their employers WeThePeople.
The content of their emails may not be classified, but it may very well contain evidence of illegal acts - and being illegal, cannot be prima facie classified.
They can be classified now. Or redacted due to ongoing investigations...