Not just turn it on without their approval.

Provide a way to resolve the issue in the very foreseeable situation where someone doesn't read the emails an add it.

Is it possible that you use email differently than most people? I virtually never actually check my inbox. I'm either reading an email that I knew was coming (e.g. an order confirmation with a shipping link) or I'm searching for something specific. So no matter how many emails Google sends I'm unlikely to read them.