How to filter out duplicate contacts in a workflow?
By default, marketing automation treats the same person in different lists as individual contacts. So, the same person can “enter” a workflow and go through it multiple times if they are in multiple lists.
Unique contacts lets you filter out contact duplicates based on whether they’ve already gone through a given workflow. Use it whenever you don’t want the same person to go through that workflow more than once.
The filter has a positive (green) and negative (red) connector. When a contact enters the element the first time, they’ll go down the positive path. If they’re in a different list and enter the workflow once again, they’ll go down the negative path.
This element does the filtering automatically, so there are no user-configurable options. All you need to do is add the element to the workflow wherever you want to start filtering your contacts.