Two mail instances on the same node

Ok, bummer. Maybe a sanity check is in place when one installed 2 mail instances on the same node? For now it can be done easily and no warning is issued. So my guess was it could be done…

Can instances of whatever application be transferred amongst Nodes?

Are there other services that can only be installed once on a node?


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I know it hits hard and this issue will be raised again and again. The reason it is still not solved is that during clone two Mail instances are necessary.

Installing an instance does not mean its services are running (and racing for the same port…).

We need to enforce some cardinality check in the Software Center.

Yes applications are expected to support clone/move operations, otherwise they have a bug.

Those that bind to well known ports: Mail and Samba for example. Check the documentation: it is an important fact that must be stated. If not, it’s a docs bug.


Hi @davidep

Actually, the mail situation would be MUCH simpler, and would still allow two mail servers on one host, both “reachable” via Port 25…

The same solution could also be used for Web - or is already in use for such.

The key to this is the fact that both very common internet protocolls allow for a name-based “routing”. No one accesses a mail server by IP, a DNS FQDN is often used, and usually a simple one, eg: mail.domainname.tld or www.domainname.tld.

SSH, rsync and a lot of “technical” protocolls, on the other hand, are often equally used by FQDN or IP, often IP, as it is shorter. This basically disallows named based internal routing.

An example with NethServer 7:

2 Internal Mailservers, one for mail.domain1.tld, the other for mail.domain2.tld.
A third “Mailgateway”, also NS7, using mail forwarding by name…

Containerization, like NS8 uses, makes this all on a single host (node) possible, but also migration to other nodes in the cluster, while also providing the option to double check the situation before committing!
(Race conditions like above are a classic!)

Special care would be needed when alölocating names, SPF, MX and other DNS entries, but it’s possible and works rock solid (Like most NS7 stuff, :-)! ).

IPv6 would alleviate a lot of problems, and introduce a lot of new issues (Not exposing the internal architecture to the Internet), but IPv6 has been implemented since over 20 years, but still hasn’t really “arrived”. We still need IPv4.

My 2 cents

Simpler? Not so much… Multiple account domains under the same Dovecot configuration is not so simple.


Who said under the same dovecot?
You’re forgetting containerization…

A Dovecot container pro Domain, an additional one for the “routing”…


My 2 cents

I tried Nginx without success… Alternatives?


In NS7 Postfix worked fine (But needs a dedicated Postfix basically, although more correct is that a Postfix could be Master, other “slaves”)…

In NS8, the master node would “know” which nodes do this task, and could “prepopulate” the config fields and present them as such to the cluster-admin for OKing… :slight_smile:
This “workflow” could be triggered by the admin creating a second mail-node (Service)…

Something like this (Taken from NS7):


Webmail, eg with Roundcube, works well with a reverse porxy.

For Mail clients this becomes a bit more difficult, but also possible with a bit of creative planning / programming.

One example / Suggestion: RADIUS can include accessible ressources for connecting clients.
Users connecting as would be connected to the Dovecot handling “”, a user connecting as would be connected to Dovecot server 2, handling

RADIUS, with a SSO or AD background would work, all the more reason to include RADIUS!

My 2 cents


Multiple domain, with separate userbases and separate mail instances on separate notes will or will not be possible in NS8 at “stable lunch”.

  • No (neverthless the why…)
  • Yes
  • We still don’t know.

Please, do not derail from options, dev team.

For all the adopters: multiple userbases on the same host (or cluster) is ISP level product/service. I don’t think that it’s currently a goal for NethServer.

I recall the roadmap is still published here: Trello

IIUC what you’re talking about is Mail “multi-tenant”.

It is not in the roadmap from here to stable. The current Mail module goal is feature parity with the NS7 one, and is still not reached but is planned for 1Q 2024.

If the world does not end in 2024 we can discuss plans for the NS8 future too :wink:


Answer now is “no”. It was way less time consuming writing that :slight_smile:


And way less educational, I like a more elaborated answer. We are here to learn :wink:


:face_with_hand_over_mouth: you are both right!