Does Mail in the Box support IPV6 only mail server? I do believe IPV4 is obselete, so I subscribed to a super cheap VPS at $2.50/month with IPV6 only.
I can’t be definitive (my box is dual stack) but I don’t see why not! There seems to be a preference for IPv4 only amongst the forum, so there’s less experience, but all the subsystems handle IPv6. I can’t see anything that is IPv4 only. (… waits for another reader to point out something obvious that I missed … 
)
A few questions before you leap into things. Are you reasonably technical? Does your ISP open all ports? Are you guaranteed a fixed IP address? If the answers are “yes” - give it a go.
(Re fixed address, it might be conceivable but it is not practical to operate email using DDNS. You really do want a fixed address.)
There will be one thing that the install instructions do not cover - reverse DNS entries. For IPv4, your ISP does all the work - you only have to tell them the DNS name of your box. But for IPv6, RDNS is handled by “delegation”. You set a flag at the ISP and the ISP and passes reverse queries to your authoritative name server - so you have to set your box up with appropriate information. (Things will “work” without RDNS but will score very poorly for spam, you’ll have trouble sending to anyone.)
Setting up reverse entries is not difficult, but it’s a manual process. You need to be happy using editor and the command line. I wrote some how-to notes on another thread - those were for dual stack boxes, so some minor details will by wrong, but the how-to-build-IPv6-reverse-entries should be correct. Feel free to PM me.
it is not and it will not be for quite some time to come
Probably not the best idea, especially for an email server. Because there are still many mail servers out there that are IPv4 only, to which your IPv6 only server will not be able to talk to.
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My ISP being a wireless broadband provider gives me two IPs, one IPV4 and one IPV6. I noticed my IPV4 is actually a CGNAT but my IPV6 is a public dynamic IP. I know Virtual Box lacks IPV6 support, as my Ubuntu cannot detect my IPV6. Without IPV6, I am forced behind an IPV4 CGNAT, and my only way is to use a cheap VPS due to budget constraints but I noticed many VPS providers such as Lightnode permanently block port 25. Their customer support told me SMTP is outdated and going to be replaced by whatsapp. So, I decided to run on my own mail server.
If you don’t run the email server at home it doesn’t matter whether you are behind CGNAT or not, because the email clients can connect to your email server via CGNAT just fine. CGNAT is only an issue if you want to run services from home. But running an email server at home wouldn’t have worked anyway, even without CGNAT…
- Most ISPs do block port 25 by default
- Most of the IPv4 ranges used on residential connections are on blacklists by default
- Dynamic IPv4 addresses and dynamic IPv6 prefixes are on blacklists by default
- You can’t set up PTR records for dynamic addresses, which in itself would cause your emails to be blocked by most email providers
Well first level supporters… 
That’s fine, but I would recommend using a VPS provider that offers you both IPv4 and IPv6. Otherwise you can only send or receive emails to / from servers which are also using IPv6. Unfortunately, even in 2023, there are still many email providers out there that have not implemented IPv6. Honestly, in my opinion, you would be better off with an IPv4-only server than the other way around.
I have a question as I am a little bit confused about technicalities 
Now, let me simple and say if port 25 is blocked, and port 25 is SMTP port.
But I am primarily going to receive mail, and POP3 is port 110. Correct me if I am wrong?
On the DNS MX record say in Namecheap, which port is used 110 or 25?
Lets say:
example.com. IN MX 10 box.example.com.
box.example.com has port 110 open. So, can I receive mail?
I plan to create a tunnel to my Mail In A Box server using localtonet as reverse proxy. What ports these tunnels need to run on? Port 25, Port 110, and Port 80? Correct?
Your server must be accessible on port 25 in order to receive emails from other email servers.
POP3 can be used for email clients to download emails from your server. This has nothing to do with receiving emails from other email servers.
No, that’s not how it works.
Not sure what you men by creating a tunnel, but as I said in my previous post, if you are running your server on a VPS you don’t need to do any special things on your home network. That would only be necessary if you would run the server from home.
However, your VPS must of course meet all the requirements for sending and receiving email, like e.g a public IPv4 address, to be able to communicate with email servers that are IPv4-only, or having port 25 open (inbound and outbound), to be able to communicate with other email servers at all.
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would you mind telling me which VPS it is? I am interested in a cheap IP6 only one
Thanks for explaining it to me. I now understand. My ISP only blocks outbound SMTP port 25 (obviously to prevent spam) and not inbound SMTP port 25 (which allows my mail server to receive email). I tried receiving email from Gmail, Outlook, Cloudflare, etc and yes, I can receive email. However, when I try to send email, I get a timed out but if I change wireless broadband providers, I get “spam IP”. This confirms my first ISP blocks outbound port 25, while my second ISP does not block but still their IP range are in spamhaus list.
So, for sending email, I will need a smart host. Do you know what is a good smart host that is cheap, or free that is compatible with Mail In A Box? I googled up and there is mailjet, postmarkapp, improvmx, and many others. Has anyone here used them? What is your experience?
Therw two such VPS providers, one vpsmalaysia and its $2.50 / month. The other is LightNode and is $2 / month.
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