Confirmation Email from Webform Submission
This functionality is available out of the box with Webform.


On the webform node page, click on the "Webform" tab
From the webform tab, click on the "E-mails" tab
Click on the "Component value" radio button and select the component of the webform that captures the email address.
Click on the "Add" button
On the next page, you can set the Subject, From Address, From Name, and E-mail contents.