“How could he not know? He sent and received emails to her.”
And the fact that he used a pseudonym is evidence that he knew it was wrong.
He should have known it was wrong.
He signed HR 1233 which amends the Federal Records Act in 2014 when Hillary's server was running.
Prohibits the President, the Vice President, or a covered employee (i.e., the immediate staff of the President and Vice President or office advising and assisting the President or Vice President) from creating or sending a presidential or vice presidential record using a non-official electronic messaging account unless the President, Vice President, or covered employee: (1) copies an official electronic messaging account of the President, Vice President, or covered employee in the original creation or transmission of the presidential or vice presidential record; or (2) forwards a complete copy of the presidential record to an official electronic messaging account of the President, Vice President, or covered employee not later than 20 days after the original creation or transmission of the presidential or vice presidential record.
Where are those copies?