function moometric_dynamic_attachments( $cf7 ) {
    $submission = WPCF7_Submission::get_instance();

    if ( !$submission ) {
        return false;
    }

    $post_url = $submission->get_meta( 'url' );
    $post_id = url_to_postid( $post_url );

    if ( !$post_id ) {
        return false;
    }

    $field = get_post_custom( $post_id );

    if ( !$field ) {
        return false;
    }

    foreach ( $field as $key => $id ) {
        if ( strpos( $key, "_acf_uploadfield", 0 ) === 0 ) {
            $file = get_attached_file( $id[0], false );

            if ( !$file ) {
                continue;
            }

            $name = basename( $file );
            $temp = sys_get_temp_dir() . "/" . $name;
            if ( copy( $file, $temp ) ) {
                $submission->add_uploaded_file($key, $temp );
            }
        }
    }

    return true;
}

add_action( 'wpcf7_before_send_mail', 'moometric_dynamic_attachments' );