To be honest, I dunno how spam actually works, I dunno how random people get my email but they all have that unsubscribe thing (Except the ones with obvious scams) but does it actually work? I have the idea it just more trouble than it's worth.
Sometimes it works. Sometimes it doesn't. It always worked for me. And there are some email subscriptions that won't go away I just have to keep unscribing until it stop. Or you can just set it as SPAM so it won't have to clutter your inbox again.
this is why i avoid clicking or following those unsubscribe links, it just tells them you are "listening" and they can verify your email is good to either sell to someone else, or spam you from a different place
Just set a filter with your email provider (Gmail and Outlook/Hotmail have this) so that those spam messages are always sent to spam or deleted. That way you don't have to worry about unsubscribe button snafus and your inbox remains clean.