How to get the `comment_post_ID`?

I have extracted the reply emails. The original emails are saved as CPT and work as Tickets in my plugin. I want the reply email to go as a comment to the original email.

 for($j = 1; $j <= $total; $j++){
            $mail = $emails->get($j);
//This checks if the email is reply or not and if the email is reply make it comment to its original post. 
    if ((!empty($mail['header']->references )) && ($mail['header']->references ) == ($mail['header']->message_id )
                {
                    $comment_array = array(
                        'comment_content' => $mail['body'],
                        'comment_post_ID' => ,

                    )
                    wp_insert_comment($comment_array);
                }
           }

I have distinguished the reply email and original email but I don’t how to keep those emails as comments to the original email.
This is how my wp_insert_post looks like:

$post_array = array( 
            'post_content'  => $mail['body'],
            'post_title'    => $mail['header']->subject,
            'post_type'     => 'faqpress-tickets',
            'post_author'   =>  ucwords(strstr($mail['header']->fromaddress, '<',true)),
            'post_status'   => 'publish',
            'meta_input'    => array(   
                'User'      => ucwords(strstr($mail['header']->fromaddress, '<',true)),
                'From'      => preg_replace('~[<>]~', '', strstr($mail['header']->fromaddress, '<')),
                'Email'     => $mail['header']->Date,
                'ticket_id' => $mail['header']->message_id,   
            ),
        );
      //wp_insert_post( $post_array );

If anyone knows how to do it. It will be a great help.