Gmail SMTP + XOAuth mystery

Question

Hi everyone, I am using python smtplib and xoauth and I am trying to send an email. I am using the code posted by Google: http://code.google.com/p/google-mail-xoauth-tools/source/browse/trunk/python/xoauth.py

I am actually authenticating against Gmail and i get this reply

reply: '235 2.7.0 Accepted\r\n'

after sending my XOAuth string as expected (http://code.google.com/apis/gmail/oauth/protocol.html#smtp)

When I compose an email I try to send I get the following error

reply: '530-5.5.1 Authentication Required. Learn more at                              \r\n'

reply: '530 5.5.1 http://mail.google.com/support/bin/answer.py?answer=14257 f10sm4144741bkl.17\r\n'

Any clue?