USPS mail forwarding vs ???

We have used the USPS forwarding service for over 10 years. You can have the mail forwarded to any address that will accept it (some campgrounds, another home address etc.) We go to the same area each winter and have a P.O. box there. So we have our home mail forwarded to the P.O. Box. Only problem we have had is several times at the beginning our post office where the box is will reject our forwarded mail and send it back to our home address, of course when that returned mail gets back home it is again forwarded to the P.O. box. 2 or 3 times we have had our mail go around in circles for over 3 weeks before we could get it straightened out. What we learned to do is as soon as we get to our winter area, notify the post office where our box is to open our box to allow mail to come there. It's not suppose to be necessary to do that, but it works. As someone else said all mail will not get forwarded, so if you should have any mail that is stamped do not forward you will not get it.