(That's the year 2009. Sorry, only four mailboxes here.)
Just for fun, I did an image search on DuckDuckGo (a private alternative to Google) for tucson mailboxes. I found a few 2009 photos from real estate agent Gabrielle Kamahele Rhind, Fun With Mailboxes in Tucson AZ!
This Tucson Mailbox Art blog started in 2012. So someone else had the weird idea first. Kudos to Gabrielle.