Automatically Link Contacts to Cases

We're using Dynamics CRM Online 2015 and the Dynamics for Outlook add-in.   The Outlook add-in is configured to automatically create Contact records for senders of emails that are being tracked.

In addition we have added a Contacts sub-grid to the Case records in Dynamics, so that Contacts (in addition to the Primary Contact) can be linked to Cases.

Are there suggestions for how the Contact record for the original sender of an email that is being tracked in Dynamics can automatically be linked to the Case that the email thread is linked to (after manually creating the Case)?

Thanks.