Turn on confirmations to make sure recipients have chosen to join your list.
With confirmations turned on for your list, addresses will only be activated for sending after they have responded to a confirmation email from you. You can even customize your confirmation message! Confirmed opt-in is a great tool for your email campaign.
You only need to have an opt-out service to follow the 2003 American CAN-SPAM Act, but having a confirmed opt-in feature with your email campaign, you will make your recipients happier. Even though it takes slightly more time for them to click themselves into the subscribed list, they will not receive emails from you when they don't want them. This also allows you to send emails legally, to only those who are subscribed to your list. It also makes your life a lot easier, and can make your email campaign be that much more efficient.