What do I say to this person?

A person from a section of YA I visit often has been sending me email, trying to be friends. I don't really know anything about the person, or why person is emailing me. The person makes small talk but rarely says anything of substance. Three times a day, person will ask, "how are you doing today?" I don't know who the person is or why sending me email. If I say something that might lead to a conversation, the person ignores it and goes back to things like, "how are you doing today?" I don't want to be impolite, but I don't know why person is trying to have conversation with me but then barely says anything. What do I say to person? Someone else told me to be straightforward, but I am afraid the person will think I am being rude and I don't want to hurt the person's feelings.