How to resend the confirmation email?
When you import your contact list you have the option to send a confirmation email so that your contacts must confirm their subscriptions, if they don't, they fall under "unconfirmed subscribers" and won't receive your campaigns. Therefore, you can resend the confirmation.
You have access to 2 requests, once these 2 emails are sent, if the contact hasn't confirmed, you cannot resend any more confirmation emails.
To send this email, go to List -> Manage publications. Click on view of the publication and click on Resend confirmation in the "next available actions" section at the bottom of the page.