Webform: Double-Opt-In E-Mail-Address

Hi Drupal-fans,

I would like a user to confirm his e-mail-address so that I can use it for e-mail-marketing.

• The user fills out a webform including his mail-address
• he receives an e-mail with a confirmation link
• after he clicks the link, his webform-result will receive a "flag", that says "e-mail-confirmed"

I tried http://drupal.org/project/webform_confirm_email, which only allows me to send mails from within the system. But I would like to use another mail-system.

To make it short: I'd like confirmed mail addresses to be flagged as confirmed.

Any help is appreciated.