Re: IPv6 recap

But, isn't it just assigning IPV4 and IPV6 to the MX?
Example
domain.com MX mail.domain.com
mail.domain.com A ipv4
mail.domain.com AAAA ipv6

It's not correct?





Em ter., 26 de mar. de 2024 às 19:23, Alessandro Vesely <[email protected]>
escreveu:

> Hi,
>
> the IPv6 MX being secondary, no compliant sender should choose it unless
> it has
> IPv6 connections only.
>
> Best
> Ale
>
>
> On Tue 26/Mar/2024 15:36:08 +0100 Adam Augustine wrote:
> > Hello Ale,
> >
> > I am mildly surprised that you haven't seen any IPv6 traffic yet. When I
> did my
> > testing most traffic to or from the big email providers seemed to use
> IPv6 for
> > the most part. Microsoft cloud-based email exchanges (see what I did
> there?)
> > particularly stick out in my mind as being predominantly IPv6, but I
> seem to
> > recall a fair number of Gmail connections being IPv6 as well. But all
> this was
> > a few years ago.
> >
> > I may have misrepresented the one user's reaction to my testing. He only
> > eventually noticed the IPv6 addresses when he happened to look at the
> > "Received:" headers while looking for the "Delivered-To" header. And
> this was
> > more than a year after I had started and forgotten to end my test. There
> is
> > nothing in the email addresses themselves that indicate whether it was
> > delivered via v4 or v6.
> >
> > Ah, good times,
> >    Adam
> >
> > On 3/24/24 06:00, Alessandro Vesely wrote:
> >> Hi Adam,
> >>
> >> thanks for sharing your thoughts and experience.
> >>
> >> I ended up setting two new IPv6 addresses.  One for outgoing mail, in
> ip6out
> >> and SPF record.  The other for incoming, set in esmtpd's PORT variable
> and
> >> published as a secondary MX which only has an AAAA address.
> >>
> >> Thus far neither happened to be used.  I prefer it so, because people
> is
> >> picky about unknown email addresses, and I don't send so much mail as
> to make
> >> my address(es) known.  Increasing the number of addresses worsens low
> volume
> >> senders reputation.
> >>
> >> That differs from IPv6 usage for the web, where I regularly get IPv6
> >> connection, sometimes reaching percentages as high as 4%.
> >>
> >>
> >> Best
> >> Ale
> >>
> >>
> >> On Sat 23/Mar/2024 00:49:52 +0100 Adam Augustine wrote:
> >>> Hello Ale,
> >>>
> >>> I have some practical experience with IPv6 environments.
> >>>
> >>> "Is it advisable to use different numbers (in the same /64) for
> outgoing
> >>> (ip6out) and incoming MX, esmtpd, esmtpd-msa, esmtpd-ssl, pop3d,
> pop3d-ssl,
> >>> imapd and imapd-ssl?"
> >>>
> >>> Short answer, do whatever makes things easy for you.
> >>>
> >>> Longer answer:
> >>> Despite what people say about "Everything is different in IPv6!" my
> >>> experience has been that 90% if not more of everything is exactly the
> same,
> >>> just with longer addresses. The remaining 10% or so that does change
> has
> >>> mostly to do with how IPv6 addresses get assigned in dynamic
> environments
> >>> (cases where you would use DHCP in the IPv4 world). You don't have to
> use
> >>> those functions if you don't want to. IPv6 was meant to be a drop-in
> >>> replacement for IPv4, and it actually works that way, assuming the
> >>> applications are coded correctly.
> >>>
> >>> I may or may not have tested IPv6 with Courier a few times on a
> production
> >>> system with a light but non-trivial load. It just worked. I may
> possibly
> >>> have accidentally left my test running for more than a year or so
> before
> >>> someone noticed and said something about the funny addresses.
> >>>
> >>> If you are already hosting all those services (SMTP, POP, IMAP, and
> their
> >>> encrypted counterparts) on a single IPv4 address and that is working
> for you
> >>> today, then follow the same operational pattern with IPv6. Think of it
> like
> >>> adding another network interface with a second IPv4 address. Would you
> do
> >>> anything different from what you are doing today in that scenario?
> Probably
> >>> not. So don't change anything and do IPv6 the same way.
> >>>
> >>> At least, at first. There /is/ a psychological barrier that you are
> going to
> >>> need to get over to get used to IPv6, and that barrier is just
> >>> unfamiliarity. Once you get comfortable and are used to looking at
> those
> >>> addresses as normal and fully accept that things work exactly the same
> as
> >>> they did with IPv4, start imagining what you could do if you had all
> the
> >>> IPv4 addresses you could ever possibly want and could waste them in
> >>> embarrassing ways. IPv6 gives you that, you just have a longer address.
> >>>
> >>> If it would makes your life easier to have a separate IPv4 address for
> each
> >>> service, then you can do that with IPv6.
> >>>
> >>> If it would make sense for you to have a separate IP address for /each
> and
> >>> every incoming and outgoing connection and never _ever_ re-use that
> address
> >>> again/, you can do that with IPv6. And only after 3,928 years would
> you need
> >>> another /64 subnet. And that is assuming a 100 gigabit ethernet
> network and
> >>> a single 64 byte packet representing each connection. So that's a
> lower bound.
> >>>
> >>> It is hard to break out of the "I must conserve" mindset of IPv4, so
> >>> exercises like that help open the mind to the possibilities.
> >>>
> >>> One bit of production roll-out advice I would give. You won't get
> traffic on
> >>> IPv6 until you publish the "AAAA" equivalent of the DNS "A" record for
> your
> >>> MX record. So don't create the "AAAA" record until you are ready to
> take
> >>> traffic on your IPv6 address. And when you do, set the TTL to
> something
> >>> short (60 seconds maybe). That way, if you do make a mistake in the
> >>> configuration somewhere, you can remove the "AAAA" and figure things
> out at
> >>> your leisure. Minimal impact. It is helpful in situations like if you
> forgot
> >>> to open the inbound port 25 on IPv6 in addition to the already open
> port 25
> >>> on IPv4 on the firewall. Just an example.
> >>>
> >>> Anyway, I hope that is at least somewhat useful. And thanks for all
> the work
> >>> you do to keep my email flowing. You don't know it, but some of your
> posts
> >>> have really helped me over the years.
> >>>
> >>>   Adam Augustine
> >>>
> >>>
> >>> On 3/20/24 09:18, Alessandro Vesely wrote:
> >>>> Hi all,
> >>>>
> >>>> I've always compiled Courier using the --without-ipv6 option. Now
> I've got
> >>>> some IPv6 addresses, so I'd try and enable IPv6 for mail. In order to
> keep
> >>>> behavioral changes to a minimum, I've already set IPv4 preference in
> >>>> /etc/gai.conf, and will leave courierd's ESMTP_PREFER_IPV6_MX
> commented out.
> >>>>
> >>>> What else?
> >>>>
> >>>> Is it advisable to use different numbers (in the same /64) for
> outgoing
> >>>> (ip6out) and incoming MX, esmtpd, esmtpd-msa, esmtpd-ssl, pop3d,
> pop3d-ssl,
> >>>> imapd and imapd-ssl?
> >>>>
> >>>> TIA for any hint
> >>>>
> >>>> Best
> >>>> Ale
> >>
> >>
> >>
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