This plugin does exactly what you need – Pie Register
From WordPress.org Plugin Directory:
Email Validation Hate fake emails? Make sure your users are not
registering with invalid email accounts by forcing them to click a
validation link that’s sent out with their registration email. This
sets there username to a random generated string (something like:
‘unverified__h439herld3’) so they can’t login until they hit that
validation link which will put their real username back in place
allowing them to login as per usual. Unverified registrations have a
defined grace period that will automatically delete an unverified
account after a specified period of time, so you don’t get clogged up
with those fakies. (Manage under Users > Unverified Users)