Ok, so, this company sent me spam a week ago, and the only way to opt out was to delete my account, which I did. Today they sent me spam again, urging me to delete my account if I do not want to receive more. I checked, I cannot log in to my account anymore.
This isn't going to be easy, is it? Well, two can play that game. Have a nice GDPR data access request.
"We are fully aware of our legal obligations. We see your account deletion in our system, but due to a problem in the synchronization between our account and mailing systems, the deletion did not propagate. This error will be corrected today, our colleagues are working on the problem right now. We guarantee you will not be sent mail again."
No response to my data request though. I'm going to be nice today, and not pester them with that, unless they fail their promise.