Using the Workflow module, I've got a content type that can be created by anonymous and authenticated users alike, then it goes into a review process. Upon creation, I want to email the user with a confirmation email. You may be asking, "do you want to email anonymous users too?", and that'd be a good question; the answer is "ideally, yes", but the important thing right now is authenticated users.
Ideally, we'd use the email field (field_email) as an address, but when I try to use [node:field_email] or [node:field-email] (the field itself is of type "Email", from the "email" module.), I get the error "Enter a valid email address, or use a token email address such as [node:author:mail]"
So, we decided to just use [node:author:mail], but, of course, anonymous users don't have an email and it follows that when they save the new node, they get the "Unable to send e-mail. Contact the site administrator if the site persists."
NOTE: This action is being created on the /admin/config/system/actions page, and added as a trigger; not on the "/admin/config/workflow/rules" page. For some reason, it seems like using the actual Rules module itself with workflow breaks; none of the rules we try to set up actually fire.