contact form 7—need to hide email address

my website allows guest users to make posts. they fill out their email address which gets sent to a custom field. i am then using contact form 7 with the dynamic text editor to reply to that user’s email address by pulling the data from the custom field using this code
[dynamichidden recipient-email "CF7_get_custom_field key='Author Email' obfuscate='on'"]

i used this tutorial… http://sevenspark.com/wordpress-plugins/how-to-dynamically-set-the-recipient-to-email-address-in-contact-form-7

everything works great, however when using developer tools like firebug, you can still view the person’s email address that you are sending to and this is a major problem. please help. any ideas???