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    How to solve “Our system has detected that this message does not meet IPv6 sending guidelines regarding PTR records”


    Plesk server has IPv6 address. When an email message is sent from the server to a Gmail account it fails to deliver.

    In /usr/local/psa/var/log/maillog on Linux or in C:\Program Files (x86)\Parallels\Plesk\Mail Servers\Mail Enable\Logging\SMTP\SMTP-Debug.log on Windows the following error appears:


    The email message sender receives following message:

    Remote host said: 550-5.7.1 [2a00:14e8:211:2123::2 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 https://support.google.com/mail/?p=ipv6_authentication_error for more

    550 5.7.1 information. la8si618732wjb.94 – gsmtp


    Gmail Guidelines for IPv6 are not met.


    Verify that the IPv6 address has a PTR-record from any Linux shell:

    # dig -x 2001:db8:f61:a1ff:0:0:0:80 |grep PTR

    ; IN PTR example.com

    Verify that an answer for PTR record query matches the IP obtained via the forward DNS resolution of the hostname specified in the PTR record:

    # dig example.com|grep IN|grep A


    In case these conditions are not met, contact your ISP.


    On Linux, Postfix can be configured to use only IPv4 addresses:

    Connect to the server via SSH.

    Check the current protocols:

    # postconf inet_protocols,

    inet_protocols = all

    In /etc/postfix/main.cf, replace inet_protocols=all with inet_protocols=ipv4 using a text editor (for example, vi):

    # grep ‘inet_protocols’ /etc/postfix/main.cf

    add “inet_protocols = ipv4” and add ‘#’ to “inet_protocols = all”

    inet_protocols = ipv4

    #inet_protocols = all

    Restart Postfix:

    # service postfix restart

    Ensure that the configuration is updated:

    # postconf inet_protocols

    inet_protocols = ipv4

    Source: V. CHUKWUKA

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