input: Write a function to send automated emails to a list of recipients. The function should iterate over the list of recipient emails and send an email to each address using the Gmail SMTP server. The function should print 'Email sent successfully.' after sending each email. If the recipient list is empty then the function should print 'No recipient emails provided.' and exit.
  assert send_automated_emails(["email1@example.com","email2@example.com"]) == "Email sent successfully."
  assert send_automated_emails([]) == "No recipient emails provided."
output: def send_automated_emails(recipient_emails):
      if not recipient_emails:
          print("No recipient emails provided.")
          return
      for email in recipient_emails:
          # Code to send email using Gmail SMTP server
          print("Email sent successfully.")