How can I assign a fax via email to a specific contact?

Instead of moving or linking the incoming message to the shared workgroup folder, forward the email to the shared workgroup folder and in the body of the message simply add the contact’s email address. This email address will be found by the contact’s email linking criteria and will show the fax on the contact record.

Alternatively, if the fax has a unique code / pattern you can add that to the contact’s linked email criteria (hover over the linked-email activity > click the edit icon > add the text to the “contains” option).