As your contact data often comes from different sources, from time to time you may run into duplicate or possible duplicate entries. For example, if you import a contact into your database who has already subscribed to your newsletter through an online registration form with a different email address, you will have two profiles for the same person, who would consequently receive two copies of your next email campaign.

But you do not need to worry about duplicate contacts as the Emarsys B2C Marketing Cloud can manage most duplicates automatically. First, your account has a default duplicate handling method: it treats contacts having the same email address identical and merges them automatically. It runs this duplication check every time a new contact is about to be imported into your database via a registration form or manual entry.

When you use manual or automatic contact import in the Emarsys B2C Marketing Cloud, you can select the database fields against which duplication checks are run. These are called Unique Identifiers and can be defined after you have selected the import file you want to upload. The system will treat contacts as duplicates if all the fields marked as unique identifiers match those of an existing contact.

Manual Import UI

Managing duplicate suspects

And if there is a chance that two contacts are identical, for example, they have the same first and last name but with a different email address, the Emarsys B2C Marketing Cloud may flag them as duplicate suspects. These suspect entries are listed on the Duplication Handling page in the Admin menu, where you can merge them or mark them separate entries.

Manual Import UI

First, click the Preview icon to review the profiles of the duplicate suspect contacts. To merge them, click the →← icon. This will update the details of an existing contact with those of the more recent one. But as a rule of thumb, empty fields never overwrite fields containing data, that is, fields are never deleted.

Or you can confirm that they are separate contacts by clicking the ←→ icon.


  • Do not select single-choice fields as Unique Identifiers.
  • You can avoid sending more emails to the same recipient in any campaign if you check Do not send to duplicate email addresses on the Email Settings page when setting up your campaign. With this option enabled, the only way the same contact can receive your campaign twice is when you use A/B testing and the entries belonging to the same contact are sorted into more testing groups.


In terms of duplication handling, what happens to those fields that differ in capitalization only (e.g. "Smith" and "smith")?

Contacts whose unique identifiers differ in capitalization only are considered identical, and are merged automatically.