Associate an email message with a contact who has not sent or received it.

Associate an email message with a contact who has not sent or received it.

I'm using Zoho CRM with the Mail Add-on.

I have an email message that I would like to associate with a contact who has not sent or received it, so that when I view that contact's record, I will see this message.  How can I do this?

As shown in the attachment, I see there's an "Add To" menu, but when I choose CRM Contacts I can only create a new contact, I can't add it to an existing contact.

Thanks!