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

In Salesforce, the standard email field is available on all contacts. 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 or person account). This will result in multiple audience records for that one person, one per email. (See data wizard)

Field Mappings send mapped data from Salesforce to Mailchimp whenever the related Salesforce record is edited. If you have multiple email addresses for the same Salesforce contact, the integration will update all related audience records based on any field mappings if active.

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