https://www.techdirt.com/articles/20180523/00523539885/many-those-desperate-gdpr-emails-youve-been-getting-are-violating-different-eu-regulation.shtml

As we careen wildly into a post-GDPR world at the end of this week, you've probably already been inundated with tons upon tons of emails from various companies where you either have an account or have been signed up for their mailing list. Some of these emails likely note that they want you to confirm that you want to remain on their list because of the GDPR. Others pretend they're just checking in with you for the hell of it. According to an expert in EU regulation, many of these emails probably violate another EU regulation, one designed to make spamming illegal. As for the others? They're almost certainly not necessary under the GDPR and appear to be people misunderstanding the GDPR "out of an abundance of caution."

In short, if a service already has proper permission from you, then it doesn't need to get it again. If it doesn't, it's violating EU spam regulations by asking you to give your consent to receive such messages.