Jimmy has loved this inside mailbox since before we moved in (and I have too). It doesn't currently receive our mail from outside so he uses it has his own treasure box. Around Valentines he became extra excited about it because he could put his own mail in it. I helped him put his Valentines for all our family members in the box and then he happily delivered them to everyone at our family dinner one night. His Snoopy card from the Great Grandparents and his Valentine for dad are still in there.
Here are a few of the card I actually made from the vintage ones I found online.