Sempre que tento enviar notificações no meu aplicativo rails, recebo o seguinte erro

Net::SMTPAuthenticationError (535-5.7.1 Username and Password not accepted. Learn more at                   
):
  app/models/friendship.rb:6:in `send_request'
  app/controllers/friends_controller.rb:21:in `make_friendship'

s configurações de e-mail @my development.rb são

  # Don't care if the mailer can't send
  config.action_mailer.raise_delivery_errors = true

  config.action_mailer.delivery_method = :smtp
  # Gmail SMTP server setup
  config.action_mailer.smtp_settings = {
        :address => "smtp.gmail.com",
        :enable_starttls_auto => true,
        :port => 587,
        :domain => '@example.com',
        :authentication => :plain,
        :user_name => '[email protected]',
        :password => 'secret'
  }