Hi Chuck,
You're getting that message because smtp.yourdomain.biz doesn't exist. Use mail.yourdomain.biz for both your POP and SMTP server.
Username: account+yourdomain.biz (although
username@yourdomain.biz will work in most clients too)
No special port (default should be 25)
No security options required (IP authorization is done through checking your POP mail).
Other than making sure you check your POP3 account every 5 minutes to keep your IP authorized, it should work fine (provided you ISP allows sending of mail through an external server - some do not).
(And I'd never tell anyone they "should" use their ISP mailserver... it's significantly easier to send mail when you're travelling if you can use a standard external mailserver).