I have been greeting all my professors as "Professor (last name)" in emails I send to them. I think this is normal, but at my university all the professors/lecturers use their first name when ending emails they send.
For example, if the teacher's name was "Joe Smith", they might end an email they send as follows:
This behavior is the case with all of the professors I've had, so it seems to be something that's global to the university. Should I be addressing my professors by their first name in emails? I would have done so already, but I don't want to sound disrespectful. I've looked it up but haven't found any guidelines my university gives on addressing faculty.
Also, I think this question is different from others because as far as I know, my university is an exception with all professors using their first name.