Yesterday I started getting someone else's K-Mart and Sears receipts. Today I discovered I have an account on Roblox.com. I'm going to guess that in both case

Yesterday I started getting someone else's K-Mart and Sears receipts. Today I discovered I have an account on Roblox.com. I'm going to guess that in both cases someone managed to enter not-their-email-address twice, correctly. "Valid address" really means "the person who in fact gets mail at that address asked to get that mail."