There's not really anything you can do about an individual spam complaint, aside from telling the end user and having them remove the email from their list (asi

There's not really anything you can do about an individual spam complaint, aside from telling the end user and having them remove the email from their list (aside from things that are quite obviously spam). The problem is the 'Report Spam' button is also the 'I no longer wish to receive this email' button to non-technical users. Just because you've received a spam complaint, doesn't mean that it wasn't an opt-in email. Providers never attempt to verify your email list. If you generate too many spam complaints, you get terminated. It's not feasible for a third party to get a copy of your mailing list, then somehow evaluate how legitimate it is.