CODE EXAMPLE FOR PYTHON

ValueError: There may be at most 1 Subject headers in a message

for email in email_list:
    msg['To'] = email
    server = smtplib.SMTP(host='smtp.gmail.com', port=587)
    server.starttls()
    server.login("myemail@gmail.com", "mypassword")
    server.send_message(msg)
    server.quit()
    del msg['To]  <----- Delete the subject of the message to resend.