action mailer and url generation in Rails 3.0.9

So I realize that Rails mailers need help in generating urls. I want HTML email with images served externally (no attachments) so I've set both:

  config.action_mailer.default_url_options 开发者_开发技巧= { :host => "localhost:3000" }
  config.action_mailer.asset_host = "http://localhost:3000

and two things happen in my mailer template:

1. It hates the use of image_tag. Just barfs with an action view template error
2. url_for does nothing for unnamed routes. shouldn't it prepend the asset_host? for assets in public?