How to confirm location address without verification code from a letter?

How to confirm location address without letter with verification code?

I have 2 properties. One property doesn't have PO Box and I can't receive letter with verification code. The second house didn't receive the letter yet, more than month.

I am registered more than month on Booking.com but I can rent on it. It's very annoying to solve this problem. Who does know any solution?

Thank you