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. Wietse
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