yahoo mail error 550, b'Request failed; Mailbox unavailable'

Question

So this code works for gmail, when i tried it on yahoo mail i get this error, (550, b'Request failed; Mailbox unavailable')

mail = imaplib.IMAP4_SSL(imap_server)
mail.login(emaill, pwd)
   

# select the label to work on
print('selecting inbox folder')
    try:
        mail.select('INBOX')
        _, data = mail.search(None, '(UNSEEN)')
        mail_ids = data[0]
        id_list = mail_ids.split()
            
        for mess in id_list:
            _, data = mail.fetch(mess, '(RFC822)')
            for response in data:
               if isinstance(response, tuple):
                  print('preparing email body.........')
                  msg = email.message_from_string(response[1].decode('ISO-8859-1'), policy=email.policy.default)
                        
                        # open_links(msg)
                        body_of_email = 'Hi' 
                        email_from = msg['from']
                        email_to = msg['to']
                        subject = msg['subject']
                        mssg = MIMEText(body_of_email, 'plain')
                        mssg['Subject'] = subject
                        mssg['From'] = email_from
                        mssg['To'] = email_to
                        mssg['Message-ID'] = msg['Message-ID']
                        try:
                            # msg.add_header('reply-to', email_to)

                            s = smtplib.SMTP_SSL(host=smtp_server, port=port)
                            # .starttls()
                            s.login(user=emaill, password=pwd)
                            
                            s.sendmail(emaill, msg['From'], mssg.as_string())

the above code won't work but I change the message to let say 'hey you, it works, so am thinking there is a problem with the MIMETest construction, any help please