code: def mail_logger(app, level = None):
      
      credentials = None
      if app.config['MAIL_USERNAME'] and app.config['MAIL_PASSWORD']:
          credentials = (app.config['MAIL_USERNAME'], app.config['MAIL_PASSWORD'])
  
      secure = None
      if app.config['MAIL_USE_TLS']:
          secure = tuple()
  
      # @todo: move to configuration
      config = dict(
          mailhost=(app.config['MAIL_SERVER'], app.config['MAIL_PORT']),
          fromaddr=app.config['MAIL_DEFAULT_SENDER'],
          toaddrs=app.config['ADMINS'],
          credentials = credentials,
          subject='Application exception',
          secure = secure,
          timeout=1.0
      )
  
      mail_handler = SMTPHandler(**config)
  
      if level is None: level = logging.ERROR
      mail_handler.setLevel(level)
  
      mail_log_format = '''
      Message type:       %(levelname)s
      Location:           %(pathname)s:%(lineno)d
      Module:             %(module)s
      Function:           %(funcName)s
      Time:               %(asctime)s
  
      Message:
  
      %(message)s
      '''
  
      mail_handler.setFormatter(logging.Formatter(mail_log_format))
      return mail_handler
docs: Get mail logger
      Returns configured instance of mail logger ready to be attached to app.
  
      Important: app.config['DEBUG'] must be False!
  
      :param app:         application instance
      :param level:       mail errors of this level
      :return:            SMTPHandler