input: Write a python function to send an email using smtplib.
  assert send_email("smtp-mail.outlook.com", 587, "sender_address", "sender_password", "receiver_address", "Subject: Test\n\nThis is a test message.") == "Email sent successfully"
  assert send_email("smtp.example.com", 587, "example_sender@example.com", "example_password", "example_receiver@example.com", "Subject: Example\n\nThis is an example message.") == "Email sent successfully"
output: def send_email(smtp_server, port, sender_email, sender_password, receiver_email, message):
      import smtplib
      try:
          with smtplib.SMTP(smtp_server, port) as server:
              server.starttls()
              server.login(sender_email, sender_password)
              server.sendmail(sender_email, receiver_email, message)
          return "Email sent successfully"
      except Exception as e:
          return str(e)