Multiple instances of mail-in-a-box

Hello guys!

Does Mail-in-a-Box support having more than one mail server running, for backup and availability purposes?


Email just doesn’t work in a manner that makes either of those things reasonable.

Hi lpossamainz,

MIAB isn’t setup to handle multiple servers, but it could be done. You’d need to do plenty of manual setup, and you’ll learn heaps along the way … it’s not something that MIAB or the forum could easily help with.

One option - your service provider might be able to provide some kind of (transparent) failover of your virtual server. That’s between you and them. It would be easy for you, but would come at a $ cost.

It is possible to have multiple mail servers (flagged by multiple MX records for your domain). When a sender can’t reach the first, the sender should try the other listed servers. This is perfectly doable but way outside the scope of MIAB. If you want to go down that path, you’re on your way to becoming an email expert :slight_smile:

I am going to take this one and discuss it from a MiaB viewpoint to explain why it simply wouldn’t be reasonable to do so.

So yes, you could have a second, third, fourth, etc. MiaB server set up to catch emails in the case of the failure of the first, but then what actually happens when that server goes down for a nano second and your email is not delivered to that server? With the second MiaB MX, the email will then be delivered to the second machine. But then what? You need to check email in two completely separate mailboxes. Sounds like it is starting to get complicated, eh? Add a third or fourth ‘backup’. So in any given day you could end up with emails on 4 different servers caused simply by network congestion! Now things are really getting out of hand.

Let’s go back to discussing how email is designed to work … if a sending server cannot deliver an email due to the server being down, network congestion, whatever really … properly configured email servers will retry sending that email, Usually they will retry for at least 2 days but many providers actually retry for up to 5 days! Unless you are sipping margarita’s on a tropical island beach for a week’s vacation, you are going to know that there is an issue and fix it well before emails simply fail.

Now on the subject of well, what if … and you really DO want a second MX? The thing to do is to have a backup MX service. Either a MTA (Not a complete mail server stack, like MiaB) that you’ve deployed, or a service that you’ve hired specifically for this purpose. The backup MTA will catch emails and hold them until they can be delivered. This is how a majority of providers used to handle this, but even this is going the way of the dodo bird, because frankly email is usually just too reliable.

So in conclusion, it really seems that running multiple MiaB instances doesn’t really help. I haven’t even touched on the logistics of doing so – keep in mind that each MiaB instance expects to be primary DNS for the domain’s that it hosts. So it is much more complicated even than having multiple MiaB servers up and running.

There is however one thing that EVERY MiaB user should do to reduce the chance of having a single point of failure event!

Using MiaB as designed does have a major drawback as it is a single point of failure. To avoid this, and insure that your emails will be queued for redelivery in the case of a short term outage you need to set up Secondary DNS.

I CANNOT stress how important this is.

For more information please read:


The problems with things like failovers is that you have to actively monitor the failover, which is something a bit more than trivial. The failover will rarely be used, so if the failover is failing, how to determine? It’s not a big deal if you are a professional administrator and this is your day job, but when you are just a self-hoster, this can become a serious problem if, say, the failover is eating delivered messages. How would you ever even know about it? Because that is what happened to me. It was a fun experiment, but ultimately it isn’t really needed.

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Agree very strongly with alento on this. Email will function adequately if your server has short-term outages BUT ONLY if senders can get your MX details - for this the sender needs your DNS records.

If you’re looking to register a domain, I’ve been very happy with - who have the (for me) the significant advantage of including an easy to use secondary DNS server service. Now, if my server is down (and so my DNS is down), senders can still get my details via gandi’s server, and I’ll receive the emails when my server comes back.

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I’m not brave enough to try it out for production, it all looks a bit R&Dish to me - but WildDuck appears to be trying to address this, and has some interesting features to boot.

I’ve been curious about Wild Duck for years, has anybody here actually given it a go and got any opinions about it?

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