Unable to send an email: Our system has detected that this message does not meet IPv6 sending guidelines regarding PTR records

Refers to:

  • Plesk 12.5 for Linux
  • Plesk 11.5 for Linux
  • Plesk 12.0 for Linux
  • Plesk 12.5 for Windows

Created:

2016-11-16 13:06:04 UTC

Modified:

2017-01-31 22:03:24 UTC

2

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Unable to send an email: Our system has detected that this message does not meet IPv6 sending guidelines regarding PTR records

Symptoms

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 in Linux or in C:\\Program Files (x86)\\Parallels\\Plesk\\Mail Servers\\Mail Enable\\Logging\\SMTP\\SMTP-Debug.log in Windows the following error appears:

ipv6_failed_after_I_sent_the_message./Remote_host_said:_550-5.7.1_[ipv6______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._hg7si388602wjb.61_-_gsmtp/

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

Cause

Gmail Guidelines for IPv6 are not met

Resolution

Verify that the IPv6 address has a PTR-record:

# dig -x 2001:db8:f61:a1ff:0:0:0:80 |grep PTR
;0.8.0.0.0.0.0.0.0.0.0.0.0.0.0.0.f.f.1.a.1.6.f.0.8.b.d.0.1.0.0.2.ip6.arpa. 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
203.0.113.2
2001:db8:f61:a1ff:0:0:0:80

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

Workaround

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

  1. Check the current protocols:

    [root@server ~]# postconf inet_protocols
    inet_protocols = all
  2. In /etc/postfix/main.cf , replace inet_protocols=all with inet_protocols=ipv4 using a text editor (for example, vi):

    [root@server ~]# grep 'inet_protocols' /etc/postfix/main.cf
    inet_protocols = ipv4
    #inet_protocols = all
  3. Restart Postfix:

    # service postfix restart
  4. Ensure that the configuration is updated:

    [root@server ~]## postconf inet_protocols
    inet_protocols = ipv4
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