Any new constituents added via JustGiving will have their Channels and Purposes set as below and will not automatically be added to your Constituent List used to sync with MailChimp:

• Channels: All set as undefined
• Purposes: any opted into will be set according to your JustGiving settings
• Preferred contact method: Do Not Contact

Reference: JustGiving - settings and mappings overview

The MailChimp integration currently syncs where the Preferred Contact Method is not set to Do Not Contact, so if you would like any newly added people from JustGiving to be added to your MailChimp audience, then you should update their Preferred Contact Method to email. As long as your consent statement says that you are intending to send emails to them then this should be fine to do.

(Though for transparency purposes you should log that decision in your organisation's GDPR documentation)

You can find your newly added constituents by two methods:

• Activity List, filtered by Activity Type = Fundraising Page Created, and Date Added
• Transaction List, filtered by your JustGiving Payment Method, and Constituent Date Added

Once you have located your newly added constituents via JustGiving, you can download the List to Excel, delete any columns that are not required leaving just the Constituent Number column. 

You can then add the Constituent Number to the Channels & Purposes template from the Data Preparation Template, set the Channel and Preferred Channel, and Upload this to the File Uploader.

This Knowledge Base article runs through how to use the template: Updating Channels & Purposes with the File Uploader

Once completed, the constituents will be available in the List used to sync with MailChimp (assuming there are no filters that may rule them out of the data selection).