Guest users are external people you can invite to missions and participate.

Guest users do not share the same domain name in the email address and will probably belong to another company. You can invite people to mission selections etc to let them participate. To prove external users (GUESTS) to a mission, you must add the users to the access list.

Admin users can only be admins once they have been trusted. To do this go to:

Settings >> Security

Here you see your own company DOMAIN for example: "example.com". If you want to invite an external user to be trusted then you need to add this user's domain to that list of trusted domains. For example, add "xyz.com".