Several mail tokens are not being replaced.

I just sent a test email to myself via the "Send an Email" activity. I included all available tokens. The following tokens were not replaced and were left as the plain text {} format:

{contact.contact_type} {contact.contact_sub_type} {contact.sort_name} {contact.on_hold} {contact.is_bulkmail} {contact.world_region} {contact.group} {contact.tag}

In addition, the following tokens were replaced with null instead of real data:

{contact.user_unique_id}

(Is this supposed to mean contact_id or drupal uid?)