Hey Jesse, This is sort of controversial and you'll get some people saying very vehemently that you should never do this ever, for various reasons of interoperability or strong opinions about how the internet works. But instead, here's my take from an operational perspective...
I personally would keep forcing mail to Gmail over IPv4, and I do indeed do this on my own hobbyist systems. Every time I spin up a new VPS and forget this, I notice it rather quickly because of bouncing mail. Not only are they quicker to block IPv6 mail overall (IMHO), they also are more likely to block IPv6 mail from IPs without rDNS, and mail that lacks either SPF or DKIM authentication. Their filters are evolving and it feels as though their IPv4 blocking is catching up a bit -- more likely to block unauthenticated IPv4 mail today versus a year or two ago, but that doesn't really mean it suddenly became easier to send over IPv6. I blogged about this a couple year ago - nothing you don't already know, really - https://www.spamresource.com/2020/11/honestly-dont-send-to-gmail-over-ipv6.html - but recently that article got linked to on Reddit and a bunch of nerds made noise that I don't know what I'm talking about and that they can get mail to Gmail over IPv6 just fine. So, YMMV. (My point is that it's not impossible, but it is annoying and that it has exacting, but unclear requirements.) Cheers, Al Iverson On Fri, Aug 12, 2022 at 11:26 AM Jesse Hathaway via mailop <mailop@mailop.org> wrote: > > Back in 2013[1] we changed our mail config to force MX lookups for gmail > to only use IPv4 addresses. We made these change after hearing reports > of higher spam scoring when sending mail via IPv6. Would anyone from > Google be able to comment as to whether forcing IPv4 is still needed? > Yours kindly, Jesse Hathaway > > > [1]: https://gerrit.wikimedia.org/r/c/operations/puppet/+/79753 > _______________________________________________ > mailop mailing list > mailop@mailop.org > https://list.mailop.org/listinfo/mailop -- Al Iverson / Deliverability blogging at www.spamresource.com Subscribe to the weekly newsletter at wombatmail.com/sr.cgi DNS Tools at xnnd.com / (312) 725-0130 / Chicago (Central Time) _______________________________________________ mailop mailing list mailop@mailop.org https://list.mailop.org/listinfo/mailop
