Assuming you're not with me on moving from opt-in to opt-out—I suspect that ship has sailed—what I'd suggest is this.
Number one, find a better way of carving out those one-off emails that are written by a real person.
Monsieur Le Roux was right that there are often exemptions that we can rely on, but there are uncertainties around them. For example, if you read the definition of “personal relationship”, it's a nightmare. It's just impossible. I have no idea what it means, and I'm a lawyer with nearly 20 years' experience.