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Friday, 25 May 2018 10:52

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

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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 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:

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 from any Linux shell:

 

# 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.

Workaround

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

inet_protocols = ipv4

#inet_protocols = all

Restart Postfix:

# service postfix restart

Ensure that the configuration is updated:

 

# postconf inet_protocols

inet_protocols = ipv4

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