Just received a nice note from the post office today for an overweight package. I didn't realize this rule so thought I'd give you a heads up if you mail PIF packages from home a lot using stamps like I do. This includes priority boxes, too.
"If your item weighs more than 13 ounces, and you have affixed postage stamps, you must take it to an employee at the retail counter of a Post Office."
"If your item weighs more than 13 ounces, and you have affixed postage stamps, you must take it to an employee at the retail counter of a Post Office."