[
 {
  "doctype": "Newsletter", 
  "lead_source": "All", 
  "message": "This is a test newsletter", 
  "send_from": "admin@example.com", 
  "send_to_type": "Lead", 
  "subject": "_Test Newsletter to Lead"
 }, 
 {
  "contact_type": "Customer", 
  "doctype": "Newsletter", 
  "message": "This is a test newsletter", 
  "send_from": "admin@example.com", 
  "send_to_type": "Contact", 
  "subject": "_Test Newsletter to Contact"
 }, 
 {
  "doctype": "Newsletter", 
  "email_list": "test_custom@example.com, test_custom1@example.com, test_custom2@example.com", 
  "message": "This is a test newsletter", 
  "send_from": "admin@example.com", 
  "send_to_type": "Custom", 
  "subject": "_Test Newsletter to Custom"
 }
]