Is it ok to put emoticons in emails to teachers/AOs?

Is a student deemed “childish” or “incompetent” if they have one or two emoticons in an email to a teacher or AO? This question came to my mind because I was sending an email to one of my previous teachers telling him about my freshman experience so far and sending him well wishes, and I used some smiley faces (like : ) and : D). This might have been okay because he and I talked a lot last year and I enjoyed his class and he liked me as a student, but what about emoticons in emails to new teachers? Or teachers I don’t know that well? Or AOs?

Teachers, when emailing informally, fine. AOs, I would not.

You would not use them in a cover letter for job application, would you?

If it’s someone you know relatively well and it’s a personal type email, it’s fine.