Dodgy Source "X institution" or "X person" when return email address doesn't match
Dodgy Links, says one thing url actually goes to another
Advertises some service like checking your computer for viruses or selling some other un-asked for product
I used to work reception/clerk at a small business and would handle all the incoming email traffic. It couldn't just be ignored because there were plenty of legit messages/inquires from persons and institutions I was unfamiliar with. So a level of discernment had to be applied on a case by case basis. I never got scammed in the year or so I was there, but the lady who worked the same position on the days I was off did.