Dec 16 05:01:07 www postfix/local: 9DA341110183: to=<firstname.lastname@example.org>, orig_to=<email@example.com>, relay=local, delay=0, status=sent (delivered to mailbox)
The mail is delivered, but to root. Have you set any redirects in postfix for the webmaster account? Please have a look in the postfix aliases file.
Try to create another mail account that is not a webmaster address. If this account is working properly we know thats not a general problem in mail delivery.