At this point, once you have added a data source and wish to add another—meaning you want to import new contacts into your audience—you will need to decide whether to unify (merge) contacts that share matching data across your different sources, such as email or phone number.

You can combine those contacts you identify as duplicates because they have identical values (e.g., the same email or mobile phone number). This will automatically remove duplicates that exist across your various data sources. Once a merge attribute is set up in your project, it cannot be removed.

All contacts with the same values in different data sources for the selected merge attributes will be automatically merged. Contacts with null values will not be merged.

You also have the option to not merge and import contacts with the same email or phone number (if you do not select this value as the key field).

If you import duplicated contacts and want to send a SMS campaign, you will be able to choose Send or not to duplicated contacts.