If the "Preferred Name" merge field is used, and the constituent record does not have a "Preferred Name" listed, then this will be replaced by a blank. that is awkward for the email to then say "Dear ," but there are some first names that should have the preferred name. seems silly to have to run a query to separate people with a preferred name or not instead of saying preferred name and being able to tell it to do a first name if there is not a prefeerd name. or first name and pull the preferred name if they have one