Using personalization strings created by selecting the data extension can be used to include the warehouse ID in their tracking parameters so that the third-party system can identify the subscriber. Personalization strings are placeholders that can be inserted into emails or landing pages to display information from data extensions or lists, such as subscriber attributes or custom fields. Personalization strings can also be used as tracking parameters in links or image tags. Reference: https://help.salesforce.com/s/articleView?id=sf.mc_es_create_personalization_strings_by_selecting_a_data_extension.htm&type=5 https://help.salesforce.com/s/articleView?id=sf.mc_es_tracking_parameters_for_links_and_image_tags.htm&type=5