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Are there any SMTP relays (or something?) that can receive on Ipv4 and send out on IPv6?

Discussion in 'Servers and Enterprise Solutions' started by BlizzardX, Jun 9, 2019.

  1. BlizzardX

    Wise Guy

    Joined: Oct 19, 2002

    Posts: 2,201

    Location: Auckland, New Zealand

    Hi

    I've got a homelab with email servers for family use; its far cheaper than Exchange or Google for all the family plus I get to run other stuff on the VM hosts.

    I've got a single static IPv4 but a /56 static IPv6. I'd like to move my servers off the loadbalanced IPv4 address on to various IPv6 addresses to free up the IPv4. I also use MXGuard Dog as an MX email filter which has served me well.

    What I'm wanting to happen is the following:

    Email sent from external > IPv4 address to MXGuard Dog > IPV4 to a Relay(?) > IPv6 out to home lab

    Email sent from internal > IPv6 from homelab > IPv6 in to relay/smarthost (DKIM signing etc.) > IPv4/6 to external

    Is this at all possible? Effectively I'm looking at relaying emails from an IPv4 routing to IPv6... I'm considering a cheap hosted instance near NZ at ~$60 per year if required but I'd rather use cheaper service if possible.

    Currently I'm using SocketLab for my smart host relay but I can't find out whether the basic service has access to IPv6 and I don't think they will accept emails and then forward on...

    Anyone got any thoughts? Another static IPv4 would obviously be the easier option but right now my ISP is charging lots for a small range.

    Cheers

    Chris
     
  2. Caged

    Capodecina

    Joined: Oct 18, 2002

    Posts: 23,073

    Surely IPv6 will be used as the first preference anyway? Or can MXGuarddog not deliver to IPv6 destinations?
     
  3. BlizzardX

    Wise Guy

    Joined: Oct 19, 2002

    Posts: 2,201

    Location: Auckland, New Zealand

    Sorry, yes I should have clarified that MXGuarddog cannot and is not yet moving to IPv6. I'm toying with Sophos UTM to do email filtering from the lab itself but I'm aware of the maintainability of UTMs and certainly non-paid products. I'd rather stick with MXguarddog if I can possibly but happy to look at other options.

    I presume a relay can receive and send out via different protocols if its setup to?
     
  4. BlizzardX

    Wise Guy

    Joined: Oct 19, 2002

    Posts: 2,201

    Location: Auckland, New Zealand

    So personally I'm a dimwit. I realised that I do not need it fully on IPv6; I only wanted to free up ports 80 and 443 which I could route through to IPv6 via cloudflare (for IPv4 only connections) and keep port 25 on IPv4 for SMTP as I don't need that port for anything else!

    I am still curious about any MX relays that use authorisation and can relay on either IPv6 or IPv4...
     
  5. Caged

    Capodecina

    Joined: Oct 18, 2002

    Posts: 23,073

    Presumably it would be pretty straightforward to run sendmail in a cloud provider of your choice, and configure it to relay in this way. You wouldn’t explicitly need to tell it to use IPv6 - if the server it is relaying to has a AAAA record then it should prefer it.