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I set up and ran a couple of mail servers on ipv4 address on amazon ec2. These addresses were previously blacklisted and it took some work to stop some emails from getting blocked. The other problem is that amazon limits you to only 5 elastic ipv4 addresses per region (an elastic ip is equivalent of a static ip).

I plan to set up other mail servers on ec2. To avoid the problems above, I want to set up the mail servers with ipv6 out of the box and I want that ipv6 address to be the main static ip address for the machine and basically ignore the ipv4 address (except for when using ssh, etc.).

Is this possible? Will I run into problems with some mail servers not being able to talk to my ipv6 machine because they are ipv4? If so, is it possible to advertise the non-static ipv4 address instead? I'm not sure how this all works. I'm new to ipv6.

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It is definitely possible - you don't have to change much, you just need to update the DNS entries for your mailserver to point to that IPv6 address.

But whether you really want to do it, is another question... there are still tons of mailservers out there which do not have the means to contact an IPv6 address - none of those domains would be able to send an email to you!

I would rather go with a couple of mailrelays: you have a number of public ipv4 mailservers which do nothing but forwarding emails to the correct server, which stands in a private subnet.

Or you go with an hybrid aproach - mailrelay for ipv4 and directly accessible via IPv6. But if you use IPv4, I would really recommend using a static IP.

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  • Yeah, I was coming to the same conclusion. Have a public ipv4: for all the different mail servers I have set up. Now why do you suggest a couple of mailrelays? For redundancy? Commented Nov 5, 2020 at 21:16
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    First of all because I don‘t know anything about the size of your Domains... if the expected load ( sent / received Mails per day ) is small, you might be good with a single relay. Commented Nov 5, 2020 at 22:38
  • "none of those domains would be able to send an email to you!" --- would they be able to receive email from the user if it's form an IPv6-only server? Commented Mar 26, 2021 at 22:20
  • in terms of communication, it doesn't matter in which direction the mail goes. Your server is unable to talk IPv4, you need an mailrelay which can talk both protocols to be able to send or receive emails to / from an IPv4 server. Commented Mar 27, 2021 at 11:00
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Yes, its possible to run a mail server on an IPv6 address. You use my IPv6 address to run a mail server but as many mail servers such as Outlook do not support IPv6 yet and if you have to receive email from your friends who use Outlook, then in order for them to be able to send you email, you have to use cloudflare mail routing to redirect mail from their IPv4 mail servers such as Outlook to your IPv6 mail server.

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