How to allow incoming IPv6, disable only outgoing IPv6?

At the advice of vele to respond to recurring Spamhaus listings of my MIAB, I want to turn off outgoing IPv6 smtp connections. In the question Disable IPv6 on my MIAB-Configuration I found the instructions at Sending Email over IPv4 with Postfix - RamNode which say to change inet_protocols = all to inet_protocols = ipv4 in /etc/postfix/ However, when I do that, the status checks page of the web interface says that incoming ipv6 connections are disallowed as well. I’d rather not do that, because presumably MIAB dns is saying that my server is available at the IPv6 address. Does anyone know how to disable only outgoing IPv6 connections? Thanks.

Change back inet_protocols = all

You need to insert smtp_address_preference = ipv4

for outgoing mail to prefer ipv4

This is good for your mail not ending up in spam if you dont have rDNS for IPV6 or you fear that outgoing IPV6 ends up in spam, which is most frequently the case as they dont care about ipv6 sending servers.

You will still get incoming mail via IPV6 from IPV6 capable servers.