Like what other said, you should be happy as you received a legitimate proof in paper, means this comes from a genuine sender. In email, a lot of things can be done, phishing, scam, identity theft, etc.. specially if the email came from someone you don't know or worst pretend to be someone you knew, but if the provider of email service is legit, you can first check their business website and that they also offer the direct mailing service such as this one digitekprinting.com/direct-mail . They send your this document by mail, also to prove that they have the right person they are dealing with.