I found out that Gmail is rejecting mail sent from our system to Gmail. Earlier this was working just fine but now for some reason it don't. Mails from Gmail comes trough perfectly.
I get following error message: "mx.google.com #550-5.7.1 [2002:d444:97a::d444:97a 16] The sender does not meet basic ipv6 550-5.7.1 sending guidelines of authentication and rdns resolution of sending 550-5.7.1 ip. Please review 550 5.7.1 https://support.google.com/mail/answer/81126 for more information. 2si864792lar.66 - gsmtp ##"
We have mydomain.com that is hosted by our web-server service provider. Mydomain.com points to our public webpages. We also have server.mydomain.com that is the "address" to our server. This server.mydomain.com is our SBS server and our outbound
mail server. Mydomain.com DNS, hosted by our service provider, includes records that point server.mydomain.com to the IP of our server at server.mydomain.com. This resolution works correctly. Our server.mydomain.com have dedicated IP just for our server.
Also our PTR record for reverse DNS in server.mydomain.com is correctly working according to http://mxtoolbox.com/ReverseLookup.aspx and http://www.zoneedit.com/lookup.html. Ipv6 is not used as far as I know.
I have tried to study the link provided by DNR. Reasons may be SPF-record. We have SPF-record and all the time have had. Our SPF though is TXT record. SPF (type 99) records can not be done in our service provider's DNS system (which is Plesk 11.0.9). This
feature comes to Plesk 11.5.30. Microsoft tool here http://www.microsoft.com/mscorp/safety/content/technologies/senderid/wizard/default.aspx dont find our SPF record but mxtoolbox.com and few other does.
Can I draw a conclusion that Microsoft's tool looks for only SPF Type 99 record but discards TXT formed SPF records?? Does Gmail behave the same way??
I am pretty much lost here.. What could be the reason that keeps Gmail blocking our mail?? Any ideas..??
And does anybody know any contact details to Gmail or Google in these kind of matters