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Well the absolute first thing that springs to mind is that you need a reverse DNS entry configured for that IP, and I can see that `2002:c063:e73a::c063:e73a<wbr />` <a href="https://www.ultratools.com/tools/ipv6InfoResult?ipAddress=2002%3Ac063%3Ae73a%3A%3Ac063%3Ae73a" rel="ugc">does not have one</a>. You either need that in your own DNS with appropriate glue records, or set it via your ISP, which is usually the easier route as anyone worth using will have a UI for doing just that. That IP is registered to Hurricane Electric, so I'm guessing this is a 6 to 4 gateway. Solve that and I suspect you'll be on your way. Disabling IPv6 is just giving up rather than solving it!
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@squinky<br />
The op is not using ip v6 Gmail is retrieving it from the email header which is showing the ip v6 of the nic on exchange <br />
It is a known issue
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Hello <br />
When i try to send an email to gmail address from my Exchange Server i receive the rejected message with these details:<br />
<br />
[2002:c063:e73a::c063:e73a<wbr />] Our system has detected that this message does not meet IPv6 sending guidelines regarding PTR records and authentication. Please review <a href="https://support.google.com/mail/?p=IPv6AuthError" rel="ugc nofollow">https://support.google.com/mail/?p=IPv6AuthError</a>&nbsp;for more information . g93si24123900qtd.124 - gsmtp <br />
<br />
I tryed many solutions but the problem not solved <br />
my spf tested :ok <br />
i test the health with <a href="http://www.mail-tester.com" rel="ugc">www.mail-tester.com</a>&nbsp;and i received the score 9/10 so evrything it's OK <br />
i disabled the IPv6 also not solved<br />
<br />
can you please help me to resolve it !
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Hello 
When i try to send an email to gmail address from my Exchange Server i receive the rejected message with these details:

[2002:c063:e73a::c063:e73a] 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=IPv6AuthError for more information . g93si24123900qtd.124 - gsmtp 

I tryed many solutions but the problem not solved 
my spf tested :ok 
i test the health with www.mail-tester.com and i received the score 9/10 so evrything it's OK 
i disabled the IPv6 also not solved

can you please help me to resolve it !

Exchange to Gmail Problem

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.

Exchange

An email client, email reader or more formally mail user agent (MUA) is a computer program in the category of groupware environments used to access and manage a user's email. A web application that provides message management, composition, and reception functions may internally act as an email client; as a whole, it is commonly referred to as webmail. Likewise, email client may be referred to a piece of computer hardware or software whose primary or most visible role is to work as an email client. Email clients can also have other systems, like calendars, notes and contact managers.