Webform Module can't send email from user anonymous
Anonymous users can absolutely submit webforms. On the Form Settings page under submission access, there are permission checkboxes for each role. You can use Captcha or Mollom to help prevent spam submissions.



The error you're having seems like you have SMTP misconfigured. Are you currently using the SMTP module? If so, run a test to send an email to yourself. If that fails, then it's definitely the problem.