IPv6 sending guidelines regarding PTR records and 550-5.7.1 authentication

Cuando terminamos de configurar un servidor en linux, es frecuente encontrarse con el siguiente error.

Comando:

sudo sendmail -v -Am -i myname@gmail.com 

Salida comando:

myname@fx1:/etc/mail$ sudo sendmail -v -Am -i myname@gmail.com;
myname@gmail.com… Connecting to aspmx.l.google.com. via esmtp…
220 mx.google.com ESMTP v1si55415385wja.21 – gsmtp

EHLO staging.mydomain.com
       250-mx.google.com at your service, [2a01:4f8:212:27c8::2]
       250-SIZE 35882577
       250-8BITMIME
       250-STARTTLS
       250-ENHANCEDSTATUSCODES
       250-PIPELINING
       250-CHUNKING
       250 SMTPUTF8
       STARTTLS
       220 2.0.0 Ready to start TLS
       EHLO staging.mydomain.com
       250-mx.google.com at your service, [2a01:4f8:212:27c8::2]
       250-SIZE 35882577
       250-8BITMIME
       250-ENHANCEDSTATUSCODES
       250-PIPELINING
       250-CHUNKING
       250 SMTPUTF8
       MAIL From:myname@staging.mydomain.com
       250 2.1.0 OK v1si55415385wja.21 - gsmtp
       RCPT To:myname@gmail.com
       DATA
       250 2.1.5 OK v1si55415385wja.21 - gsmtp
       354  Go ahead v1si55415385wja.21 - gsmtp
       .
       550-5.7.1 [2a01:4f8:212:27c8::2] 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  https://support.google.com/mail/?p=ipv6_authentication_error for more
       550 5.7.1 information. v1si55415385wja.21 - gsmtp
       myname… Connecting to local…
       myname… Sent

Solución

Entrar en el fichero de configuración /etc/postfix/main.cf

Cambiar inet_protocols = all por inet_protocols = ipv4

Reiniciar el servicio con el siguiente comando:

 service postfix restart 

Comprobar cambios

Comando:

postconf inet_protocols 

Salida comando:

inet_protocols = ipv4