On Sun, 9 Jul 2017, Wietse Venema wrote:
This is how three years ago I solved IPv6 problems for all domains
that have Google as an MX host.
/etc/postfix/main.cf:
smtp_dns_reply_filter = pcre:/etc/postfix/smtp_dns_reply_filter
/etc/postfix/smtp_dns_reply_filter:
# /domain ttl IN AAAA address/ action, all case-insensitive.
# Note: the domain name ends in ".".
/^\S+\.google.com\.\s+\S+\s+\S+\s+AAAA\s+/ IGNORE
This drops all AAAA records from Google MX hosts, effectively forcing
Postfix to deliver over IPv4.
I adopted this because their PTR lookups did not distinguish between
'try again' and 'does not exist', causing them to reject legitimate
email.
Thanks, this seems to be working well for me.
Scott
