Ask me email, but don't force me to verify it before letting me in. While I'm browsing, show me a prominent warning that my email is not yet verified. Include my email address in the warning so that I can catch possible typos.
Edit: I do like the recommendation of showing them the email they're waiting to validate so that they can see typos.
It's an API where you give it the user's email address and they tell you if they think it's real or not. I have it such that if it's not risky I bypass the "verify email" step.
Not sure how long the API will be around and it's pretty slow but for now at least it's free.