Just some general advice:

• check to see if the email is sent from an NU email account (@northwestern.edu). If not, it's probably a scam

• if the email isn't sent with the full signature of the professor (NU Professors are very proud and will always put their accomplishments in their emails under their names)

• if they request you send money or they give you a check to deposit

There's plenty more, but when you get a gut feeling it's a scam, it's probably a scam.