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Need help resolving sendmail issue
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Need help resolving sendmail issue

Hi VPS Gurus,

First of all apology for the ignorance, I'm quite new in the mail dimension. i have a case where by gmail rejecting mail sent from my VPS server (using plain php mail function - sendmail system)

here's a sample email from gmail

----- The following addresses had permanent fatal errors -----
(reason: 550-5.7.1 [2405:4200:203::17f:6916 16] Our system has detected that this)

----- Transcript of session follows -----
... while talking to
<<< 550-5.7.1 [2405:4200:203::17f:6916 16] Our system has detected that this
<<< 550-5.7.1 message does not meet IPv6 sending guidelines regarding PTR records
<<< 550-5.7.1 and authentication. Please review
<<< 550-5.7.1 for more
<<< 550 5.7.1 information. uc3si6226495bkb.312 - gsmtp
554 5.0.0 Service unavailable

Final-Recipient: RFC822; [email protected]
Action: failed
Status: 5.7.1
Remote-MTA: DNS;
Diagnostic-Code: SMTP; 550-5.7.1 [2405:4200:203::17f:6916 16] Our system has detected that this
Last-Attempt-Date: Wed, 18 Dec 2013 17:03:46 +0800

My setup is... Domain is registered with Godaddy with A records pointed to my VPS server's ip
Then my VPS server is sending mail using the built in sendmail.

My problem now is if i use native php mail function to a gmail email account, it's not being received by the recipient, however for other recipients it's going in.

I tried reading but couldn't seem to figure out how to do it. i know google is our best friend but with lots of info about ipv6 ipv4 rdns, my head is blowing apart. Hope someone can guide me to the right path for my scenario. Thanks and Advance Merry Christmas to all.



  • Judging by the error, seems like you don't have RDNS set on your IPv6.

    Thanked by 1aolee
  • You need reverse dns set for you ipv6 address. This must be done through your vps service provider. Your vps control panel may have a feature where you can do it, if not then you'll need to open a support ticket with the provider.

    Thanked by 1aolee
  • @nunum/@sleddog Thanks for the quick response. i don't need to do anything on Godaddy am i correct to say that?

  • aolee said: @nunum/@sleddog Thanks for the quick response. i don't need to do anything on Godaddy am i correct to say that?

    Correct. Reverse DNS is handled by your VPS provider.

    Thanked by 1aolee
  • @sleddog, hi sorry for more questions. i emailed my vps provider and i was informed i have a solusvm. a bit confused some article i see in google is saying i need to have my own nameserver? can't i just input a value on the rdns inside the solusvm then it will work right away?

  • Say for example your IP is and your server's hostname is You have an A record set in Godaddy DNS: ->

    In SolusVM, in the network config, you click to set reverse DNS for the IP and enter:

    It'll take a while to propagate. When it does, you'll have reverse DNS: ->

    When your server sends an email, it identifies itself as "". The receiving server (e.g. Gmail) does a DNS lookup on that hostname and gets IP It then does a reverse DNS lookup on and gets "". Forward DNS and reverse DNS match, Gmail is happy :)

    Thanked by 1aolee
  • Thanks selddog! ipv4 rdns setup is complete. i assume its the same case for ipv6 so ive already added AAAA record in Godaddy, and added the hostname, just waiting for it to propagate so i can add an rdns entry in my vps's solusvm. Many thanks!

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