The sandwich was unremarkable—lukewarm and not quite melted, like a college freshman’s late-night microwave snack rather than a true grilled cheese. But I have thought about the sandwich every week since I ordered it, because the food truck that made it won’t stop emailing me.

First came the receipt. Then the expressions of gratitude, offers of deals. “Thanks for your visit!” one email screamed. “Get FREE FRIES!!” another offered. I do not want your free fries, food truck. What I want is to be left alone.

The emails keep coming because I paid for my grilled cheese with a credit card using the food truck’s Square credit card machine. Even though I never agreed to be put on this restaurant’s email list for all eternity, by virtue of swiping my card in that specific Square card reader, I apparently signed up to be hounded, spammed, and annoyed for the rest of my life.

If you’ve used a credit card at a retail establishment in the past five years or so, you probably know what I mean. You bought a pair of earrings at a jewelry stand? Now you’re on a list. Purchase a lemon from a roadside “honor system” fruit stand? You’re on a list. I’m on lists for the pottery place where I once bought a Christmas gift, and the fast food joint where my kid gets his dinosaur-shaped chicken nuggets.

Once you give your email to any Square vendor, you are defaulted into receiving automated receipts and promotions from every participating Square vendor you visit.

My inbox has become so clogged with marketing spam that I’ve switched to the Gmail layout that filters “Promotions” into its own ignorable tab. It is by far the most populated tab in my email. If I were into inbox zero, I’d be apoplectic. (For what it’s worth, I’m not. I’m on the record as having more unread emails in my inbox than anyone else Atlantic journalist Taylor Lorenz could find—a dubious honor.)

Obviously, Square did not create this hell on its own. Buy anything online and you’re probably on that retailer’s list, too, unless you carefully unchecked a box at the exact right moment. Even Square’s physical point-of-sale competitors do this, making the deluge of emails impossible to escape. But since Square’s payment machines are the most ubiquitous by far, it is therefore the biggest clogger of my inbox.

When I asked a representative from Square what was going on, the answer surprised me: Apparently, I had consented to receive automatic receipts and promotions from any company that uses a Square point of sale machine the very first time I ever entered my email into one of the Square readers. This is not something you have to do; you can use Square payment machines and never enter your email, and you'll avoid all automated receipts. But, once you give your email to any Square vendor, you are defaulted into receiving automated receipts and promotions from every participating Square vendor you visit.

Let me be clear: If that was me giving my consent, I didn’t understand what I was agreeing to. And that is not informed consent.

I do not remember what store I was in when I first entered my email into Square’s system, or even what year it was. What I do know is that I had intended to receive email updates from that business specifically—not from every business that uses the same payments machine for ever and ever as long as we both shall live.

Once I entered my email, my credit card was linked to my email, and my email served as consent to put me on the list of every Square vendor I visit using that credit card. This is a very intentional business decision, one Square touts to its vendors as a way for them to get extra business and make more money, capitalizing on the scale and reach of Square’s email lists to market directly to their customers without much hassle. In order to send out promotions to Square customers, vendors pay a small fee. This is one of the perks Square offers small business—without having to invest in massive direct-to-consumer marketing infrastructure, indie vendors can reach their audience.