development.rb

...
  # ActionMailer Config
  config.action_mailer.perform_deliveries = true
  config.action_mailer.default_url_options = { host: 'localhost', port: 3000 }
  config.action_mailer.raise_delivery_errors = true
  config.action_mailer.perform_caching = false
  # MailCatcher gem settings
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = { :address => "localhost", :port => 1025 }
...

gistfile1.txt

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production.rb

...
  # ActionMailer Config
  config.action_mailer.perform_deliveries = true
  config.action_mailer.raise_delivery_errors = false
  config.action_mailer.perform_caching = false
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = {
    :address   => "smtp.sendgrid.net",
    :port      => 587, # ports 587 and 2525 are also supported with STARTTLS
    :enable_starttls_auto => true, # detects and uses STARTTLS
    :user_name => ENV["SENDGRID_USERNAME"],
    :password  => ENV["SENDGRID_PASSWORD"], # SMTP password is any valid API key, when user_name is "apikey".
    :authentication => 'login',
    :domain => ENV['DOMAIN_NAME']
  }
...