Sample session log output showing the error with smtp.set_debuglevel(1):

send: 'ehlo <mysmtpserver>\r\n'
reply: b'250-<mysmtpserver> Hello [myIP4address]\r\n'
reply: b'250-SIZE 53248000\r\n'
reply: b'250-PIPELINING\r\n'
reply: b'250-DSN\r\n'
reply: b'250-ENHANCEDSTATUSCODES\r\n'
reply: b'250-STARTTLS\r\n'
reply: b'250-AUTH GSSAPI NTLM\r\n'
reply: b'250-8BITMIME\r\n'
reply: b'250-BINARYMIME\r\n'
reply: b'250 CHUNKING\r\n'
reply: retcode (250); Msg: b'<mysmtpserver> Hello [myIP4address]\
nSIZE 53248000\nPIPELINING\nDSN\nENHANCEDSTATUSCODES\nSTARTTLS\nAUTH GSSAPI NTLM
\n8BITMIME\nBINARYMIME\nCHUNKING'
send: 'STARTTLS\r\n'
reply: b'220 2.0.0 SMTP server ready\r\n'
reply: retcode (220); Msg: b'2.0.0 SMTP server ready'
send: 'ehlo [mymachinename]\r\n'
reply: b'250-<mysmtpserver> Hello [myIP4address]\r\n'
reply: b'250-SIZE 53248000\r\n'
reply: b'250-PIPELINING\r\n'
reply: b'250-DSN\r\n'
reply: b'250-ENHANCEDSTATUSCODES\r\n'
reply: b'250-AUTH GSSAPI NTLM LOGIN\r\n'
reply: b'250-8BITMIME\r\n'
reply: b'250-BINARYMIME\r\n'
reply: b'250 CHUNKING\r\n'
reply: retcode (250); Msg: b'<mysmtpserver> Hello [myIP4address]\
nSIZE 53248000\nPIPELINING\nDSN\nENHANCEDSTATUSCODES\nAUTH GSSAPI NTLM LOGIN\n8B
ITMIME\nBINARYMIME\nCHUNKING'
send: '<base64encodedaccountnamedata>==\r\n'
reply: b'500 5.3.3 Unrecognized command\r\n'
reply: retcode (500); Msg: b'5.3.3 Unrecognized command'
send: 'QUIT\r\n'
reply: b'221 2.0.0 Service closing transmission channel\r\n'
reply: retcode (221); Msg: b'2.0.0 Service closing transmission channel'
Traceback (most recent call last):
  File "sendtestmail.py", line 172, in <module>
    announcement.sendMail(password)
  File "sendtestmail.py", line 97, in sendMail
    smtp.login( self.getShortAddressList()[0], password )
  File "c:\Python35\lib\smtplib.py", line 730, in login
    raise last_exception
  File "c:\Python35\lib\smtplib.py", line 721, in login
    initial_response_ok=initial_response_ok)
  File "c:\Python35\lib\smtplib.py", line 627, in auth
    initial_response = (authobject() if initial_response_ok else None)
  File "c:\Python35\lib\smtplib.py", line 664, in auth_login
    raise SMTPAuthenticationError(code, resp)
smtplib.SMTPAuthenticationError: (500, b'5.3.3 Unrecognized command')

due to missing AUTH LOGIN here as previously described...