Then they just fill up the junk folder until you run out of space on your email server. I had to turn junk filtering off as it kept classifying a lot of legitimate emails as junk (such as bills from my utility company or bank related emails)
Often there's an 'unsubscribe' link at the bottom of such an email, and despite many assuming it doesn't actually work, it has worked in my case.
Now, if only there was a way to disable the 'Google Pay Statement' I get each month, which has no such unsubscribe link, and I never use Google Pay at all (never have, prefer Samsung Pay when it works)