Realted to this question How should I address a professor in the US? I have a question how to adress the professor in the US in my concrete situation. In the last E-Mails I wrote "Dear professor ..." and "Kind regards, Aleksana last name", and he had always responded with "Dear Aleksana",..."Best regards, Marius."
What to do now? Shall I address him by his first name now? I.e. shall I respond with "Dear Marius,"...."Kind regards, Aleksana"? Or shall I continue adressing the professor by his last name?