GMail Setting for Rails Mailer

application.rb

config.action_mailer.default_url_options = { host: "yourdomain.com" }
config.action_mailer.raise_delivery_errors = true
config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
  address: "smtp.gmail.com",
  port: 587,
  domain: "yourdomain.com",
  authentication: "plain",
  enable_starttls_auto: true,
  user_name: ENV["GMAIL_USERNAME"],
  password: ENV["GMAIL_PASSWORD"]
}