How to send emails in Rails in production environment (heroku server)

I am using this source code to send emails in heroku server but it doesn't:

config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = {
  address: "smtp.gmail.com",
  port: 25,
  authentication: "plain",
  user_name: "support@gmail.com",
  password: ENV['PASSWORD'],
  enable_starttls_auto: false
}

Is there any mistake in my source code. I want to use a free way to send email in my project Thank you