How are duplicates handled if I select multiple lists for an email?

If you select multiple lists for your email campaign, duplicate copies of email addresses will be removed before launch. This process, called deduping, occurs between step four and step five of creating an email. 
 
On the final step of the launch process you will receive a count of how many unique recipients will be mailed to. Previous bounces, unsubscribes and any duplicates found on selected lists are ignored and reflected in the total indicated on the launch page.