I should probably submit this as a product improvement request of some kind, but I'm not sure how to do that (sorry).
In a Send Email Notification action we have this checkbox to "Send individually addressed notifications".
In this example I'm sending an email to the "Created By" user, and the "Customer" (a single-user User type field in the list). If the box is checked and the "Customer" is the same person who created the list item, then the person gets two emails.
I'm thinking the product should check for and remove duplicate email addresses so that only one email is sent to any email address.
