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

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julian bonpland mignaquy
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Plesk for Linux kb: technical ABT: Group B

Applicable to:

  • Plesk for Linux

Symptoms

  • When an email message is sent from a Plesk server to a Gmail account, it fails to be delivered.

  • The following error message appears in /var/log/maillog:

    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/

    plesk postfix/smtp[17181]: connect to gmail-smtp-in.l.google.com[2001:db8:f61:a1ff:0:0:0:80]:25: Network is unreachable

  • The sender receives an email with following message:

    Remote host said: 550-5.7.1 [2001:db8:f61:a1ff:0:0:0:80 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

The server has an IPv6 address configured in Tools & Settings > IP Addresses.
Gmail Guidelines for IPv6 are not met: the IPv6 address does not have a PTR record.

Resolution

Solution I: Contact your hosting provider to set up a reverse DNS for IPv6 address.

Solution II: Apply one of the following instructions:

Configure the mail server to use IPv4 only (Postfix)

  1. Connect to the Plesk server via SSH.

  2. Find out which protocols are currently enabled with the command:

    # postconf inet_protocols
    inet_protocols = all

  3. If the output is the same, modify Postfix configuration file main.cf by executing the command below:

    # postconf inet_protocols=ipv4

  4. Restart Postfix to apply the changes:

    # service postfix restart

  5. Verify the changes:

    # postconf inet_protocols
    inet_protocols = ipv4

Disable IPv6 addresses on the server

How to disable IPv6 addresses on a Plesk server?

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