The whole thing is very suspicious. My sister had her identity stolen several years ago by someone who broke into her mailbox. She ended up $900 in the hole as a result. You should take it very seriously. You'd be surprised at what can be stolen and used. Even if it seems like junk mail, it's YOUR mail. Follow up asap and get an answer. Messing with the mail, no matter what is a crime. Don't be a victim.
Claudia