... consistently marks all the e-mails I get from my supervisor as Spam.

I wonder if my university is developing an intelligent e-mail client : )

Mine does this as well! My supervisor constantly asked did you get this, did you get this and I thought he did not send it in the beginning and just yesterday I realised he was automatically sorted in the bin... how shall I tell him (that outlook reads my mind)

Tell him not to advertise certain pharmaceuticals on his emails

Tell him to take the words "Rolex", "Free", "Viagra" and "Nigerian Bank Account" out of the subject line!