You can send your email campaign to multiple groups. You can select all the groups that you would like to send to in the Sending Options screen in NewZapp.
If sending a campaign out to a subscriber which is included in more than one group. That
person will receive only one copy of the email.
For example email@example.com is in your groups called "Group A", "Group B" and "Group C". If you select all these groups for your email campaign and even though firstname.lastname@example.org is included in all of the groups, only one email will be sent to that subscriber, instead of three.
NewZapp also automatically filters out unsubscribes from the lists.