How Do Field Mappings Work with Multiple Email Addresses on the Same Contact or Lead?

In Salesforce, the standard email field is available on both Contacts and Leads. However, you can extend this functionality by adding custom email fields, or by using packages like Salesforce NPSP, which provide a set of custom email fields.

You can add a contact or lead to Mailchimp using any email field found on the contact or lead. This will result in multiple audience records for that Contact or Lead. 

Setting up field mappings allows any mapped data from Salesforce is also sent to Mailchimp whenever a record is updated or initially added to Mailchimp. If you have multiple email addresses for the same Contact or Lead in Salesforce, the integration will update all related audience records, should the audience you are working with have field mappings set up. Each audience record corresponding to an active email address will receive the mapped data updates.

In summary, when using field mappings, any changes to the mapped fields in Salesforce will propagate to all active audience records in Mailchimp, even if they are linked to different email addresses for the same Contact or Lead. 

Note: Retrospective Apply needs special consideration with multiple emails