[pfx] Re: Should the configuration upgrade process still append "inet_protocols = ipv4"?

On 2026-05-25 7:16, Wietse Venema via Postfix-users wrote:
> I don't know that a large majority of mail servers has IPv6
> connectivity, but the way Postfix implements this feature selection
> can be improved.

Definitely not a majority, no.  From my own MX log data, I observe 
20-25% of "legitimate" mailhosts connecting over IPv6.  "Legitimate" 
here meaning those hosts that get past postscreen's bot countermeasures 
and DNSBLs.

> The "make upgrade" mechanism pre-dates "compatibility_level" which
> provides a more explicit way to manage changes in default settings
> (it would log that it is falling back to IPv4-only).

This does sound like a better way to do it.  The main.cf that lacked an 
explicit inet_protocols did have "compatibility_level = 3.11", so 
postfix would have known I expected the current default.

>> I ask because I just caught that behaviour during an upgrade test and,
>> had I not caught it, it would have knocked my publicly-IPv6-only
>> mailhosts offline.
> 
> You upgraded from a configuration that had no explicit inet_protocols
> setting?

Yes.  It didn't have "inet_protocols = all" because postconf -d said 
that was the default when I last reviewed main.cf for redundant 
settings.  I overlooked the unique handling for inet_protocols.
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