The question about weather on not Clinton knew the emails were classified or weather or not they were deemed classified after they were sent to her is MOOT. It is for this VERY reason that government officials are not supposed to use private servers to send and receive government information. You would think she knew that, actually she did know that. She just did not care.
I am a little more cynical than that. Maybe it was her way of getting classified information to our enemies. Anything to weaken or destroy the country.