Build the e-mail body text as a separate field, or even simply as a $Variable.
"Dear " &
Case ( IsEmpty ( Full_Name ) ; "Sir or Madam" ; Full_Name )
& "I am writing to you because you recently ordered a " & LastItemOrdered &
", and we wanted to know...etc"
then call that field or $Variable as the Body of the e-mail.
You can also put such a calculation directly in the body of Send Mail and you can use the ¶ symbol to add returns where needed.