These are some articles from a few years back regarding the USPS and tracking of mail. I once got a knock on the door from a US Postal Inspector and had to explain to him why I was receiving shipments of oxycodone. 

Having said that, the USPS is a scary entity and you may want to request your own personal file from the USPS or US Postal Inspectors to see if you're on their radar. You can do this with a FOIA request. But I feel like it's kind of poking the hornets net to make them look harder for you, but I've been told from multiple sources that the FOIA offices are completely separate from the law enforcement division and you should have nothing to worry about.

You can make a FOIA request from the USPS at https://anonym.to/?https://about.usps.com/who/legal/foia/ (anonymized link). However, this isn't going to tell you much. It's the postal inspectors you really have to worry about. You can request a FOIA from the Postal inspectors at this link. https://anonym.to/?https://www.uspis.gov/terms-of-service#freedom-of-information-act (anonymized link). Don't be afraid to do this. In order to get a FOIA from the postal inspectors you have to submit your information, and then they will send you something you have to get notarized within 15 days and send it back to them. They will then send you your file. You can do these FOIA requests on MuckRock, which automates and does the FOIA for you, but they become public if you use it.

The USPS uses something called "mail covers" to mark your box as one to be watched.

https://anonym.to/?https://www.nytimes.com/2013/07/04/us/monitoring-of-snail-mail.html
U.S. Postal Service Logging All Mail for Law Enforcement (link anonymized)

The other thing is that they almost never refuse a search warrant request for mail. Just do a google search for "controlled delivery" and you'll see how they do that. Sometimes they'll come to your door and ask you to sign for it. If you ordered something and the vendor didn't require a signature tell them you didn't order anything and refuse to sign for it. However, they can also insert a tracking device into the box and when it's opened, they kick down your door and raid you. This is depending on the amount you get and if it's considered enough where you're considered to be selling the drugs (I forget the term they use).

https://anonym.to/?https://www.washingtonpost.com/news/federal-eye/wp/2014/11/20/postal-service-almost-never-denies-mail-surveillance-requests/
Postal Service almost never denies mail-surveillance requests (Anonymized Link)

Finally, I wanted to share this YouTube video about how they scan for customs at the JFK mail center, which is where almost all international shipments go to nowadays.

https://anonym.to/?https://www.youtube.com/watch?v=DoY7SxrzNTc
How Customs At JFK Searches 1 Million Mail Packages A Day (Anonymized Link)

The video is well worth a watch and very informative.

There are a couple things you can do if you think your address is compromised. You can buy a DBA (doing business as) certificate from your Secretary of State and create a company name. The DBA will still be under your name, but it's cheap and it hides the package ID from scanners. Then open a PO box or a box at a UPS store or mom and pop store and use that as a cover.

You can also buy a quality fake ID and open PO boxes/UPS/mom and pop boxes and use that as your receiving address. This works well, but you need to close them eventually and move on to another ID and address.

https://anonym.to/?https://www.sba.gov/business-guide/launch-your-business/choose-your-business-name (Anonymized Link)

I hope this information helps you, but don't be scared away. The USPS receives millions of packages and letters a day and probably 90% slip through with no problem.

Hope that helps!
-pogue