said: 550-5.7.1 [*********] The IP you're using to send mail is not
authorized to 550-5.7.1 send email directly to our servers. Please use the
SMTP relay at your 550-5.7.1 service provider instead. Learn more at
550 5.7.1 http://mail.google.com/support/bin/answer.py?answer=10336
s36si7540679anh.100 (in reply to end of DATA command)
Well the Hosting company used are assigned IP to be used for Dynamic end users e.g. ADSL. and are Reverse DNS of the mail server was to a different host. not one from which email were being sent.
actions taken to fix the issue.
1. fix the reverse DNS
2. check http://www.spamhaus.org/lookup.lasso for your IP and if listed request removal.