"Unable to send email" error shown to anonymous users in Workflow action 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.
I'm assuming you're using a Rules Event "Before saving content (optionally limited to selected content types)", or some variation of a node related Rules Event.

Try to add a Rules Condition like "Entity has field" (related to that node:field-email field). After you do, that field will be available as a token you can use in any subsequent Rules Condition and/or Rules Action (where a field of that data type can be used). Your 2nd paragraph appears to me like a confirmation you don't have such Rules Condition yet (so Rules has no clue you're interested in using that eMail field).

With that, you should be able to just get it to work with the Rules module, due to which your "note" probably doesn't apply/matter anymore.