action_mailer settings for multiple sites

Hello people

I have an app that I deploy to multiple sites.
In this app, I send out email notifications.

In my actionmailer I have
ActionMailer::Base.smtp_settings = {
  :address => 'smtp.[domain]',
  :port => 25,
  :domain => 'smtp.[domain]',
  :user_name => 'noreply@[domain]',
  :password => '[password]',
  :authentication => :plain


I know in the controller, I can do a request.domain(1) to get the, but I'm not in the controller. If my understanding is
correct, this is ran once as the mongrels are starting up. How would
I determine the domain name without the request object?

Thanks for your help.