I don't see anything that hits me. Sometimes, email components are installed but don't actually send emails if configured incorrectly.
Are you certain CDONTS is properly configured. I've known of at least a few situations where a reinstall of the OS or sometimes just a reboot of the Exchange server solved similar problems.
Personally, I would try AspMail or AspEMail components. They're free, and offer a lot more functionality.
Finally, for some code that DOES work, download the test file at
http://www.pensaworks.com/prg_com.asp?v=3
there are 2 test files in the Zip file, one of which is a mailer test file, and tests for existance and correct configuration of several email components (including CDONTS) on the server.
Tim