Writing a thank you note to a professor after sitting in on a class

Applying to College
1

I am trying to write a thank you note to a professor, but I don’t know what address to send it to. Will it reach them if address it to

(their name)
(school’s address)
?

Does it make sense for me to call the admissions office to find out where to send it to?

2

Just put Prof XYZ and the college name and address. The mailroom will know.

You could add the department, if you want to be really specific!

3

Add the the professor’s department and the school’s name.