wpcf7_before_send_mail AND response message on the form page?

I let the CF7 form create a new post with “wp_insert_post” and the function: “add_action(‘wpcf7_before_send_mail’, ‘wpcf7_to_post’,1);”
This works fine, posts are created, even the confirming emails are sent.

But, when firing the function, the response message (“Your message was sent successfully”) on the form page does not work any more when clicking the submit button – without the function (unset in functions.php), the response message is shown correctly. How can I get both getting to work, the post creation AND the submission message on the form?