After I set up Community Builder 1.3.1 and configured it, I discover my site's E-mails were not being sent. I fixed that issues but are left with a numerous users who did not get the activation E-mail. How can I resend the activation E-mail so these lost users can get registered?

Thanks!

The Activation e-mail is re-sent when the user tries to login. You could manually try to login as all the users who didn't get the e-mail ...