Asking for an email up front is already too much. Let the user use your service, they'll create some "content" or "configuration" in it. Once they do that, they

Asking for an email up front is already too much. Let the user use your service, they'll create some "content" or "configuration" in it. Once they do that, they'll want to preserve / persist it, and then you can ask for an email address. They're much more likely to give you a real email address and validate it, because they're already invested.