environment.rb

  config.gem "openrain-action_mailer_tls",
             :lib => "smtp_tls.rb",
             :source => "http://gems.github.com"

smtp_gmail.rb

require 'smtp_tls'

ActionMailer::Base.smtp_settings = {
  :address => "smtp.gmail.com",
  :port => 587,
  :authentication => :plain,
  :enable_starttls_auto => true,
  :user_name => xxx,
  :password => xxx
}

staging.rb

config.action_mailer.raise_delivery_errors = true
config.action_mailer.perform_deliveries = true
config.action_mailer.delivery_method = :smtp