Even back then, I always just used throwaway emails to register on things. My actual email is reserved for real shit... Although even HR departments seem to share it with advertisers because in the last few years, I get job related ads and I've only ever given my email to real, physical people in the flesh specifically to reduce and/or eliminate spam.
On the plus side, they're legally obligated to provide a straightforward way of unsubscribing. If they won't easily let you opt out of emails, report them to the FTC.