I learned the hard way very early. I get a chuckle every time I see "hand stamp only" on a package since this is what broke the only chip I have ever had a problem with. The lady at the post office broke the chip into numerous pieces with her little stamper. Now I make them put a meter strip on everything that has a chip in it. Apparently meter stripped mail does not go thru the auto sorters either so less chance for damage. It has worked so far.