Very strange update emails from my Drupal installation.

I've received two emails from a drupal installation i've recently put online.

There are updates available for one or more of your modules or themes. To
ensure the proper functioning of your site, you should update as soon as
possible.

See the available updates page for more information:
http://www.yazoodle.net/admin/reports/updates

Your site is currently configured to send these emails when any updates are
available. To get notified only for security updates,
http://www.yazoodle.net/admin/reports/updates/settings.

My site has nothing to do with yazoodle.net.
I've seen these suspicious URLs in my logs - spam bots trying to find pages that don't exist.
But how on earth are they causing my update emails to contain the wrong URL????

I also received emails with these URLs
http://www.bradesco.com.br/admin/reports/updates - a Brazilian bank
http://www.yahoo.co.jp/admin/reports/updates - yahoo japan.

Any idea what's going on?