Freez

I’ve managed to do it but it’s… well… not very elegant.

In the backend > FC7 plugin > in Form tab, I’m placing a hidden field:

<input type="hidden" name="aux-input" id="aux-input" value=[myshortcode]>

Then, on the Mail tab, I call the field’s value. So the Subject field looks something link this:

...some text... [aux-input]

functions.php – here is what my functions.php looks like:

function printMyShortcode(){
	return 'some random text';
}
add_shortcode('myshortcode','printMyShortcode');

add_filter( 'wpcf7_form_elements', 'mycustom_wpcf7_form_elements' );
function mycustom_wpcf7_form_elements( $form ) {
	$form = do_shortcode( $form );
	return $form;
}

Thanks for reading and I hope this helps someone.

Also, I’d be really grateful if anyone can improve the solution found! ??