You must specify a valid SMTP server for CDOSYS.
Examples:
- mail.mydomain.com
- mail.mywebhost.com
- smtp.mydomain.com
- smtp.mywebhost.com
- mydomain.com
If you are using shared hosting, then try using mydomain.com. That is how one of my web hosts set it up in the past.
Also, check with your web host and ask them how to send mail via a web page. They should tell you what the SMTP server address is or if they did something unique. Also, check your web host's FAQ section. They may tell you what it is there.
And make sure they have mail installed. They may not have even installed it to prevent people from spamming. I have actually run across some webhosts who disabled e-mail on their web server!
If you don't know your SMTP server address, then that might be the problem.