DNS Mail Problems after Use of IPv6

Discussion in 'Installation/Configuration' started by sunghost, Aug 23, 2016.

  1. sunghost

    sunghost Member

    Hello,
    i switched the server and have now an IPv4 and and IPv6 Address for Shared-Hosting. Before i only have and used 1xIPv4 for all sites. On old Server i have no problems with Mail and Customerswebsites. Now i have a problem which i think came from using IPv6 too. gmail and freenet refuse mails from my sites. I searched since yesterday but cant figure out the correct setting. Now i am a bit confused and need help and clarity.
    Lets assume this facts:
    • servername = server1
    • domain for mailing on server1 = mydomain.com
    • customer 1 site = csite1.com
    • customer 2 site = csite2.com
    • Server and both IPs are at RZ-Server-Hoster, DNS is setup on other Domainprovider
    These are the settings on RZ-Server-Hoster
    • IPv4 -> Reverse -> server1.mydomain.com
    • IPv6 -> Reverse -> server1.mydomain.com
    These are the settings in DNS for mydomain.com and all other e.g. with there csite1.com instead of mydomain.com
    • A Rec server1.mydomain.com -> IPv4
    • A Rec *.mydomain.com -> IPv4
    • AAAA Rec mydomain.com -> IPv6
    • MX Rec - Hostname = mydomain.com - Mailserver = mail.mydomain.com
    • TXT - mydomain.com = v=spf1 mx -all
    These are the settings on server1
    • # hostname -> server1
    • # hostname -f -> server1.mydomain.com
    • /etc/mailname -> server1.mydomain.com
    Checks from other Host at mydomain.com
    • lookup IPv4 -> server1.mydomain.com
    • lookup IPv6 -> server1.mydomain.com
    • lookup IPv4 and IPv6 server1.mydomain.com -> IPv4 and IPv6 = ok
    • lookup server1.mydomain.com -> IPv6 and IPv4
    • lookup mydomain -> IPv6 and IPv4
    Checks from other Host at csite1.com
    • lookup csite1.com -> IPv4 and IPv6 (same as for mydomain.com)
    • so reverse lookup at IPv4 and IPv6 point to server1.mydomain.com
    On question in my mind is, have i set the DNS Recs for AAAA to fqdn or only to domain? So server1.mydomain.com and server1.csite1.com ... Should i also add an AAAA for *.mydomain.com as i setup for A Rec?
    To solve that i could switch to only use IPv4, but i think it should work with IPv6 too. So i need your help - thx.
     
  2. dimitrivisser

    dimitrivisser New Member

    Can you check your maillog ? I had the same problem with gmail refusing my emails, and the logfiles said exactly what happened. In my case it was an incorrect reverse dns of the server sending the emails. It seems that gmail uses IP6 and not IP4 if IP6 is available...

    And there was also something like caching. So if you correct it, it doesn't work immediately... What kept me busy for some time ;)
     
  3. sunghost

    sunghost Member

    Hi,
    yes i work on that since yesterday and my customers are not amused since server change :(. The Errormail from gmail shows IPv6 and while i am testing late this night i had shortly ipv4 too, but now only ipv6 which i think is the problem actualy. As far as i read and understand bynow postfix will use randomly or in cycle v4 and v6, so it could be that mails are send and other not while send over v6 ?! So yes the problem is v6..
     
  4. dimitrivisser

    dimitrivisser New Member

    Gmail forces your server to use IP6... But the problem is not IP6, the problem is bad configuration on your side... Here it works ok, after some problems...

    If you look carefully at your logfile, you can see exactly where the problem is... In my case it even gave my IP6 address that had no reverse DNS... Don't be afraid to post that part of the logfile with the response from gmail...
     
  5. sunghost

    sunghost Member

    Yes youre right, its my bad v6 dns setup :( . I think its the V6 PTR Record. But i never setup this in the DNS Console i have from my Provider, so i have to look how it works. I think i have to setup the V6 Zone First and than setup the PTR for this one V6...
     
  6. sunghost

    sunghost Member

    Any answer to my questions ?
    edit:
    i am totaly lost. Should the name in /etc/mailname match the mx record?
     
    Last edited: Aug 23, 2016
  7. dimitrivisser

    dimitrivisser New Member

    Postfix uses the /etc/mailname or the myhostname in /etc/postfix/main.cf. This name is used when SENDING email. Here it is something like vps1.mydomain.com. This name must have a A record en AAAA record. You usually can change it at the website where you registered your domain. Reverse DNS for both the IPv4 and IPv6 are the responsibility of your VPS provider. Mine has a website where I can change it myself.

    MX records are for INCOMING email... I also used vps1.mydomain.com for that. But I think you can also use another name as long as it points to the right ip address.
     

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