Great news! - The Auction Manager platform will automatically remove duplicate entries when you import your email list. Also when you send an email to multiple lists at the same time, the platform will also de-duplicate across all email lists, upon sending.
The important step to remember is: when sending to multiple lists, select all the lists before sending. Select multiple lists by holding the Ctrl key and clicking with your mouse button on each list name. If you send to one list at at time, the system cannot detect and prevent duplicates.