Exactly, so you're better off not accounting for all these special cases. As there's a never-ending list of email providers. A better approach might be to limi

Exactly, so you're better off not accounting for all these special cases. As there's a never-ending list of email providers. A better approach might be to limit the effect that a new account can have in the system. Hackernews, Reddit, Stackoverflow all do this through reputation. A new account on these systems is unable to achieve much until time is spent proving the account is being used. Thus reducing the incentive for an individual to create multiple accounts.