The one and only context in which initial capitals are used for pronouns is in traditional religious texts. God and Christ are sometimes referred to and addressed with the capitalised pronouns Him, His, You, Your and so on. You may come across this in bible texts, hymns and prayers. Your professor is (presumably) a mortal human being, so you should use lower case letters. Just curious....where did you get the idea from that using capital letters was a sign of formality and respect?