Oh, I've been getting USPS emails for a couple of months now. They usually ask me to click on some website to confirm my order. The orders they think I have can be... interesting...
I don't believe I've EVER had a real email from USPS (as until now, the couriers have never had my email address), and so they go straight to me spam folder and have been getting deleted without opening. How do you tell the difference?
It'll be sent from Ookoodook, not USPS, since they're the ones with your email address/order details. You take the tracking number in the email and enter it in the USPS website to get the tracking information (the email may have a link to automatically do this).
I won the WW Game Discworld I (Dei in Machina) by selling sausages ina bun to more than 50% of the surviving player, I showed myself as a cunning, greedy and worthy CMOT Dibbler and all I got is this lousy signature line.