Agreed. Only unsubscribe if you recognise the site as one you trust, and might plausibly have accidently subscribed to, or failed to decline news from.

If it's certainly spam, don't even open it. Doing that can alert the sender that it's reached a real address by fetching images - 'web beacons'. That will ensure you get more.

Better still, use a mail reader that ignores such images, and other tricks, and just shows you the text until you confirm it's genuine. Thunderbird does that.