how to send bcc without showing the bcc in the e-mail header?

Question

My code is as below:

def send_email(employee_list):
    password = '********'
    file = open(os.path.join(path, "html.txt"), "r", encoding="utf8")
    source_body = file.read()
    file.close()
    today = datetime.now().strftime("%d.%m.%Y")
    server = smtplib.SMTP('smtp.gmail.com', 587)
    server.starttls()
    server.login('kaan@ttttttt.com', password)

    for employee in employee_list:
        msg = MIMEMultipart()
        msg['From'] = 'noreply@ttttttt.com'
        msg['Subject'] = 'Happy new year...'
        body = source_body.replace('{{name}}',                 employee.get('name')).replace('{{anniversary}}',
                                           str(employee.get('diff'))).replace('{{today}}', str(today))

        msg['To'] = employee.get('email')
        bcc_list = ['kaan@tttttt.com', 'bora@tttttt.com']

        if employee.get('manager_email') not in bcc_list:
            bcc_list.append(employee.get('manager_email'))

        bcc_list = ','.join(bcc_list)
        msg.attach(MIMEText(body, 'html'))
        server.sendmail(msg['From'], [msg['To']] + bcc_list.split(','), msg.as_string())


    server.quit()

I can send the e-mail to all recepients but it shows the BCC recepients in the header. How can we avoid it?

I even don't have a To['Bcc'] object but it still shows the bcc_list recepients as bcc when I receive the e-mail.

Thanks.