exchangelib.errors.ErrorNonExistentMailbox: The SMTP address has no mailbox associated with it

Question

I am trying to send mail from o365 user mailbox in python using exchangelib library. I am getting "exchangelib.errors.ErrorNonExistentMailbox: The SMTP address has no mailbox associated with it" this error.

credentials = Credentials(username='username', password='password')
my_account = Account(primary_smtp_address="my organization email address",
                     config=Configuration(
                         credentials=credentials,
                         service_endpoint='https://test/EWS/Exchange.asmx',
                         auth_type='NTLM',                            
                         # server='outlook.office365.com'
                     ),
                     autodiscover=False, access_type=DELEGATE)


m = Message(account=my_account
            , folder=my_account.sent
            , subject=e_subject
            , body=HTMLBody(e_body)
            , to_recipients=[Mailbox(email_address='email address')])

m.send_and_save()

anyone know how to resolve this issue. Thanks in advance.

I am trying to send mail from o365 user mailbox in python using exchangelib library.