AWeber automatically deduplicates a list based on the subscriber's email address.
Once an email address has subscribed to a list, an email address cannot be added to the same list again.
If a person already subscribed to your campaign attempts another sign up to your list, they will automatically be directed to the Thank You Page, unless you have a specific Already Subscribed Page set for the form. With Tags, a subscriber can sign up a second time to receive additional Campaign series of messages through a different from.
If a subscriber signs up to another mailing list in the same AWeber account, the subscriber will be counted multiple time as each mailing list operates independently from each other.