Apparently I have postfix main.cf:

inet_protocols = all

so postfix is trying to send email to some Google customer using my IPv6 address but I don't have any AAAA records so I'm getting:

<support@somegooglecustomer.com>: host ASPMX.L.GOOGLE.COM[2607:f8b0:400c:c04::1a] said:
550-5.7.1 [2600:3c03::f30c:9f1f:fe98:d6c3] 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 ... tion_error for more 550
5.7.1 information. h142is1049317vkh.130 - gsmtp (in reply to end of DATA
command)

[note I changed the IPv6 address above to anonymize this message]

Should I just comment out inet_protocols or set:

inet_protocols = ipv4

Or would it be better to add AAAA records?

Is there any chance my ipv6 address could change?

Where are PTR records set?

Would you agree the lack of a PTR record for my ipv6 address is the cause for "Undelivered" from Google?

I have one stand-alone postfix server with a handful of users so this is a very simple setup. But I want maximum compatibility so I want to know if it would be better to simplify to ipv4 or do ipv6. Basically what would make me look less spammy?

I'm not sending bulk or any kind of automated anything. It's all strictly hand crafted business mail.

Also I'm assuming my SPF record should look like:

v=spf1 ip4:45.67.71.123 ipv6:2600:3c03::f30c:9f1f:fe98:d6c3/64 -all

?

Mike

Best option with IPv6 and Google seems to be to request an address pool and configure one or more addresses from it for your Linode. You can set up reverse DNS (your PTR record) through the Linode manager.

Add AAAA records and set up reverse DNS on IPv6.

I have AAA records in my DNS Manager but when I attempt to do the reserve DNS it does not pick up on the IPv6 address. I am in the middle of changing the name servers from GoDaddy to Linode

If you just added the AAAA records you'll need to wait a little bit before you can set rDNS.