Postman / Postwoman
up to 12 months in prison
Yes, from the time the mail is sent until it is received by the person it is sent to the mail is the property of the post office and therefore government property. Preventing a person from receiving their mail is theft of government property; for which you can go to prison.
Of course it is. Unless they give it to you to read. And opening it could be tampering with the mail, which could be a Federal crime.
Better not be...
Yes Yes
it depends what mail...
It is against federal law to open someone else's mail only if that mail is removed from a mailbox or from a post office or post carrier before it is delivered. If mail is delivered to your address that belongs to someone else it is not illegal to open it.
by opening it
dog sprinkler no tresspass
Although someone may receive your mail, and even open it at your specific direction, opening another person's mail (in the US) is a violation of federal law. It is rarely taken to prosecution, but it can carry a prison sentence. If you believe your mail is being opened, contact the US Postal Inspection Service.
If convicted of opening another person's mail, a person may be sentenced to up to 10 years in prison. There may also be a fine of up to $250,000.