Mailhandler: The e-mail address '*@*.com' may not create story items.

If you look at the module, you'll see it's failing the permissions check in the mailhandler_node_submit function for creating a node.
So do two things:
1. Created a user, say 'mail', gave user 'mail' the email address the mail is coming from, and gave user 'mail' permission to administer nodes (and do nothing else).
2. Filled in the from header with the word 'From' which is the mailer's account uses (not 'Sender'.)
That way, Drupal can go from the email to the user, check the user's permissions, and create the node.
That worked."