Article ID: 127946, created on Dec 29, 2015, last review on Sep 7, 2016

  • Applies to:
  • Plesk 12.5 for Linux
  • Plesk 12.0 for Linux
  • Plesk 11.5 for Linux
  • Plesk 12.5 for Windows


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:


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 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:

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

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|grep IN|grep A

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


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/, replace inet_protocols=all with inet_protocols=ipv4 using a text editor (for example, vi):

    [root@server ~]# grep 'inet_protocols' /etc/postfix/
       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

Search Words

cannot send mail gmail



Our system has detected that this message does 550-5.7.1 not meet IPv6 sending guidelines regarding PTR records and 550-5.7.1 authentication. Please review 550-5.7.1

Our system has detected that this message does not meet IPv6 sending guidelines regarding PTR records

8b661cab116c79dbe6c4ac5bbdf1c8cb 56797cefb1efc9130f7c48a7d1db0f0c a914db3fdc7a53ddcfd1b2db8f5a1b9c 85a92ca67f2200d36506862eaa6ed6b8 a766cea0c28e23e978fa78ef81918ab8 29d1e90fd304f01e6420fbe60f66f838 01bc4c8cf5b7f01f815a7ada004154a2 0a53c5a9ca65a74d37ef5c5eaeb55d7f 2a5151f57629129e26ff206d171fbb5f e335d9adf7edffca6a8af8039031a4c7 742559b1631652fadd74764ae8be475e

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