To mass / bulk send objects in Salesbox to Mailchimp follow this flow
1. Go to the preferred section
2. Open the advanced search and either search to limit the list or not
3. Click the edit icon in the bottom right corner of advanced search and select mark all
4. Click Mailchimp icon
5. Select an existing Mailchimp list OR click Add new list and fill out the form
6. Click done
All contacts connected to the object in the list will now be exported to the selected / created Mailchimp list. However, its only those that has an email added that gets exported.