That podiatry letter was going out back when I was applying to medical school over ten years ago. Sorry, not interested in crusty feet!
Seriously, if you didn't apply to WashU in the first place, then ignore that letter. It's a money-making gimmick that many schools use. You feel flattered and quickly add them to your list of schools. They send you a secondary application with a hefty fee which you pay. They send you an e-mail rejection (too cheap to send snail mail because of the cost of the stamp). They get a high number of applicants and a lower percentage of acceptees which translates to "more competitive status" for their school at your expense.
If you have money lying around and you want to frame your e-mail rejection from WashU, then apply. If not, ignore this and move on. It's kind of snarky to do this to people just because you have purchased the MCAT test takers list.