Yep, I set it to prefer v6 to test and was only noting that, at least GMail, doesn't appear to apply stricter policies around delivery any more (likely modulo your IP's existing reputation).
On 7/21/20 8:06 PM, Viktor Dukhovni wrote: > On Tue, Jul 21, 2020 at 07:54:55PM -0400, Matt Corallo wrote: > >> Still, many large sites (eg Outlook) only >> accept mail on v4, presumably for similar reasons, so there isn't much >> reason to default to prefering IPv6 for outbound mail any time in the >> next many years. > > FWIW, when you enable IPv6 support in Postfix, IPv6 is not preferred, > Postfix chooses between IPv6 and IPv4 at random, and tries to make sure > that the set of candidate nexthop IP addresses contains at least some of > each. > > So the primary reasons to not enable IPv6 outbound are: > > * Stricter policies applied to IPv6 mail by some receiving sites. > > * Some SMTP servers publishing non-working IPv6 addresses, > where the name resolves to both IPv4 and IPv6, but only IPv4 > actually works. This will latency to deliveries that happen > to try IPv6 first. > > Otherwise, if you have working IPv6 on your end, and the above issues > are not a problem, then you can enable IPv6 outbound and it should > work about as well as can be expected, modulo the above. >
