So I got an e-mail from a forum I signed up for but never visit, since it's based in Germany and I don't speak German.
Thankfully Gmail translated it well enough for me to find the unsubscribe link. The link took me to a page that gave me two options:
Schicken Sie mir künftig keine werblichen Angebote von GameStar per E-Mail.
Ich möchte auch künftig über interessante Angebote aus Ihrem Haus per E-Mail informiert werden.
As I said, I don't speak German, so I was reliant on Google Translate to tell me which one to pick. This is what Google Translate told me:
Thankfully JoTo was available in IRC to tell me that the top option actually said send me no