Dynamic recipient using custom field

I have a listings custom post type. Each listing has a custom field where an email can be entered. This is the owner of the listing and where the form will be sent.

I’m using the wpcf7_mail_components hook to dynamically set the email:

function wpcf7_dynamic_email_field($components) {

	/*
	  Retrieve email using post custom field
	*/

	// $email = get_field('listing_email', $id );
	// $components['recipient'] = $email;

	return $components;
}
add_filter('wpcf7_mail_components', 'wpcf7_dynamic_email_field');

… but I’m not sure how to get the $id of the post the form was submitted from. I tried using get_the_ID() and global $post; $post->ID but neither work.