input: Write a python function to send an email using SMTP.
  assert send_email('your_email_address', 'password', 'sender_email_address', 'receiver_email_address', 'This is a test email') == "Email sent successfully"
  assert send_email('your_email_address', 'wrong_password', 'sender_email_address', 'receiver_email_address', 'This is a test email') == "Authentication failed"
  assert send_email('your_email_address', 'password', 'sender_email_address', 'invalid_receiver_email_address', 'This is a test email') == "Failed to send email"
output: import smtplib
  from email.mime.text import MIMEText
  from email.mime.multipart import MIMEMultipart
  
  def send_email(username, password, sender_email, receiver_email, message):
      try:
          # Create the email
          msg = MIMEMultipart()
          msg['From'] = sender_email
          msg['To'] = receiver_email
          msg['Subject'] = "Test Email"
          msg.attach(MIMEText(message, 'plain'))
          
          # Connect to the server
          server = smtplib.SMTP('smtp.gmail.com', 587)
          server.starttls()
          
          # Login to the email account
          try:
              server.login(username, password)
          except smtplib.SMTPAuthenticationError:
              return "Authentication failed"
          
          # Send the email
          try:
              server.sendmail(sender_email, receiver_email, msg.as_string())
          except smtplib.SMTPRecipientsRefused:
              return "Failed to send email"
          
          # Quit the server
          server.quit()
          
          return "Email sent successfully"
      
      except Exception as e:
          return str(e)