template post Special Mail Tags

Hello
I use contact form 7 in a post template : single-machine.php

I inserted it this way:
<?php echo do_shortcode( '[contact-form-7 id="290" title="Formulaire machine OCCASION"]' );?>

In my wordpress administration > Contact, in the E-mail tab
I inserted [_post_title]

When I test the form in a post “machine” everything is fine.
BUT When I receive the mail in my webmail, it is written [_post_title] instead of the true mane of my post

Why ?
Thank you for your help