Keeping Salesforce data free from duplicates will prevent incorrect records from being synced or imported.
Outreach is designed to allow only one record per unique e-mail address. For example, if a user attempts to pull records into Outreach which have duplicate data, one record will import and map accordingly, while the other will not. When Outreach pushes new records up to Salesforce (if configured to do so), Outreach will first look for a corresponding record by using the email address as the key. If a corresponding record is found, either a Lead or a Contact, Outreach will map to the record instead of creating a new record. If a Lead and a Contact are both found (duplicates that exist in Salesforce), Outreach will take the higher of the hierarchy, in this case the Contact.