The best citation I can give you at the moment is to have you ask your local Post office. I have before with mine and you can find many anecdotes of other people talking to their own post office and the answer you will generally get from the post office is that they deliver to an address and the owner of that address has the right to receive mail so when mailing to a business the business has the right to receive that mail even if it is somebody else’s name on the mail.

Technically it does violate a couple common laws depending on the situation. You can find an explanation at shrm.org/…/can-employers-open-employee-mail-sent-…

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