We are using Microsoft Exchange 2010. From the last 3 days we are facing problem. Whenever we send email on any gmail address, Gmail rejected our emails and we receive following error message.
mx.google.com gave this error:
16] Our system has detected that this message does not meet IPv6 sending guidelines regarding PTR records and authentication. Please review https://support.google.com/mail/?p=ipv6_authentication_error
for more information. z8si7536589eee.353 - gsmtp.
Here I would like to mention that our SPF, PTR records are ok. Our IP is not blacklisted and IV6 is also disabled on our network card. Still we are unable to send email. It is requested to please resolve our issue.