I took off the backplate from the ring, to get an idea of where I want to mount it by my front door & noticed it stick to my mailbox.
Hi @Tanarus. Which model of Ring Camera do you have? You can find this information on the back of the Camera itself, on the original packaging, or on the Device Health page in the Ring App. Feel free also to share a picture of what you mean by the backplate sticking to your mailbox, that way I can take a better look and check with my team. 
@Tanarus Thanks for letting me know which model you have! Were you able to get your Doorbell installed, or did you take any photos of this magnet you were seeing? I’d be happy to take a look if you have a photo or even a video you can share. You can upload this video elsewhere, such as YouTube, and then share the link to the video in your reply.