It sounds like you are entering your email address into the send a receipt field.  That is not what you want to do.  That is why you are receiving receipts from your customers when they visit other retailers. The only reason you would receive emailed receipts from customers is if you put your address in the send a receipt field, or they put your address in the send a receipt field. That address you are typing in is now permanently associated with that credit card that was used at your facility and all future emailed receipts will go to this address.  you can click a link at the bottom of the emailed receipt that says this is not my receipt to disassociate your address from your customer's credit card.  I'm sure your customers don't want you getting all their Square receipts.

You don't need to send receipts to yourself.  they are all available from your dashboard, and if you want a receipt from your receipt printer you can simply click on the transaction in the activity menu and select print receipt.

https://squareup.com/dashboard/sales/reports/sales-summary