I've finally managed to get one of my Drupal sites set up on my Mac localhost. The LIVE site is set up to back up its database to my Amazon S3 account, and send me an email notifying me of success/failure. I assumed none of this would work on the local version of the site, but I was shocked to get a "success" email. It arrived in my Gmail inbox, and was from:

World Wide Web Server <_www@my-user-name-power-mac-g5.local>

I don't have any local email client configured, so this is messing with my head. I guess there's a lot I don't understand about email! How is this happening?