Today's Drupal frustration

I have the Simplenews and Token modules installed. I create a newsletter issue which includes links to other pages on the same site. I use the [site-url] prefix in these links. When I save the issue and send a test message to myself, [site-url] is expanded to the correct prefix for my domain. Then when I send the issue to all 600 subscribers, [site-url] is expanded to “localhost”. How embarrassing! Where do I begin to try to track down this error?

PS Short links above are using the cool new Drupal.org URL shortener http://dgo.to/