I am trying to do the same thing, with the same problem.
I have a form from Contact Form 7 sending to my secret post-by-email address. The posts never appear. If I change the form to send to my personal email account, the email arrives as expected. If I forward the output of my form from my personal email address to the secret post address, it appears successfully as a pending post, having correctly interpreted all of the various shortcodes.
This is awfully frustrating.
