When you send an email campaign to multiple databases (or segments), some contacts may exist in more than one database (or segment). To avoid the possibility of contacts receiving multiple copies of an email, Pinpointe automatically de-duplicates contacts across the selected databases/segments before sending. This way, each contact will only receive a single copy of your email. 

Pinpointe also de-duplicates contacts within a database when a contact is added to a database, so you will not have duplicate contacts within a given list.