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TechGuy_007Flag for United States of America

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Exchange 2016 getting bounce backs from google

Exchange 2016 getting bounce backs from google: gave this error:
[2601:40d:8001:dc00:5436:c102:4af2:5c68] Our system has detected that this message does not meet IPv6 sending guidelines regarding PTR records and authentication. Please review for more information . f10si1906405ioi.62 - gsmtp

I cannot figure this out for the life of me. If it's as simple as a radio box I might just cry. lol
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Edward Pamias
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Of course the information above is not for your site but maybe it will help you resolve your problem.
You basically need to contact your ISP and ask them to add a PTR record for your mail server's IP address that matches either your domain or your mail server's name. Essentially, Google's system is doing a reverse IP lookup on your IP and finding the PTR record doesn't match your domain, then refusing the connection because they expect it to be spam.

1. Goto

2. Under DNS Lookup, type the full URL your mail server hostname... say

3. In the pull down menu of "Choose a DNS Record type" select PTR and click the blue triangle button next to the input field of the full URL your mail server hostname.
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I called the ISP and they had the wrong static ipv4 and ipv6 information. I had them setup reverse DNS. I'm waiting the 24-48 hrs to see if it is resolved.
You should be fine after reverse DNS setup.
Unfortunately. The reverse DNS was setup, but I am still experiencing errors.

Post back the results on running the tool as mentioned in my previous comment.
Timeout Value      1 (default)
Your Overall Score      Lookup failed
Did your ISP charge you for Reverse SMS lookup?

Your result Indicates reverse DNS lookup is not yet made.
Then, they are not obliged to help you at all. Setup of Reverse DNS lookup is not free as a lot of re-coding work at ISP side needs to be done.
the ipv4 is good to go. the ipv6 is not. i've checked the records on and it will show for the a record but not the AAAA
There is nothing can be done on the matter and your only way out is to discuss with your ISP.
Google will not entertain you just to give you an exception for no proper reverse DNS setup and they will just think that you are a SPAM source.
Yeah, I called the ISP again and am awaiting a callback from tier 2
ptr record is setup but bounce backs are still occuring

Post back the results on running the tool as mentioned in my previous comment.
@Jackie_man your tool keeps failing. But when i run a reverse lookup on mxtoolbox, it shows my ptr being correct.
All of this is a lot easier to deal with if you use a cloud based spam filter and send your outgoing email through that. They generally take care of the reverse DNS and SPF issues. Also, do you have SPF set up on your public DNS to include your IPv6 record?
I have it running through barracuda cloud spam filter. i think i have it figured out FINALLY.
Just a note here...Based on google's guidelines, not having an SPF record or DKIM configured will cause the issue you see here. You'll also need to make sure you aren't black-listed. That said, sending mail out from Barracuda is a better solution, since it provides you with better mail security.