How does the integration work with blank values?

Mailchimp for Salesforce does not support updating fields with blank values in either direction. If you use our field mapping or Data Wizard features to update data from Salesforce to Mailchimp, any blank values will not be sent to Mailchimp. Similarly, when updating data from Mailchimp to Salesforce using field mappings, blank values from Mailchimp will not overwrite existing values in Salesforce.

This behavior is designed to ensure data integrity. As a result, the integration will never remove an existing field value. If a field is mapped and contains a value, that value will remain intact even if the corresponding field in the other system is blank.

This ensures that no critical data is inadvertently erased during the sync in either direction.