You are not. The USPS already images all mail for all persons[0]. Not to mention their use of license plate scanners[1] if you're picking up your mail at a post office.

[0]: http://www.nytimes.com/2013/07/04/us/monitoring-of-snail-mai...

[1]: http://kdvr.com/2015/03/11/mysterious-spy-cameras-collecting...