While I don't have an opinion on the quality of Apple's spam filtering, your case seems particularly interesting (and hard!) because it is not spam - it is send

While I don't have an opinion on the quality of Apple's spam filtering, your case seems particularly interesting (and hard!) because it is not spam - it is send by legitimate people with legitimate intentions. I mean, sure, it is spam to you, but I doubt you could train a decent spam filter for this situation. Maybe a whitelist, but that's about it.