Additional Headers not working

When inserting Cc: or Reply-To as mentioned on http://contactform7.com/adding-cc-bcc-and-other-mail-headers/
after saving I get a syntax error message.
If I wrote a static emailadress everything is fine.
But I want to set a Cc to the emailadress of the sender, so he/she gets a copy of the mail. And of course the reply-to should also be the emailadress of the sender. The field is required and therefore it isn’t possible that the adress isn’t set.

https://wordpress.org/plugins/contact-form-7/