Create tasks for non-Asana users

@Jon_King, You’re correct re:

… so they won’t be getting any email notification as mentioned above unless you invite them and they subsequently log in and become an Asana user.

See the following, including that entire thread, and other posts in the forum for other strategies like tagging or custom fields to indicate thrid-party assignment, but using the assignee field as below seems the best to me:

Larry