FLOSS Enterprise Email Solution

I’m looking for any FOSS or FLOSS software solutions for enterprise email. My municipality is looking to get away from a dying Exchange server and doesn’t like the idea of O365 (and similar proprietary cloud solutions).

We need a solution that can support around 400 users, be secure and provide some spam/malware prevention.

I’m searching around myself for something, but would appreciate any advice.

I have really moved away from self hosted solutions as they don’t provide good spam filtering so you still end up paying for a 3rd party filter and keeping your outbound IP off of black lists can sometimes be a challenge. This is why we moved from hosting a system to using Gsuite.

But if you are up for the challenge of running a mail sever, Zimbra is popular https://www.zimbra.com/try/zimbra-collaboration-open-source/

They have paid support options as well.

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As a side question. Have you considered using ProtonMail’s hosting solutions? Just curious.

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For my own department, separate from the rest of the county, I use G Suite just because I was tired of all the Exchange server problems they were having and I had the budget and authority to move off of their servers.

At home, I use ProtonMail for my personal stuff and that’s nice, too.

But for the county, the administrator really doesn’t want to have a cloud service with the “Netflix model” as he likes to say, meaning monthly, never-ending, fees.

The IT contractor the county uses likes open-source solutions, but I’m not sure how involved in the FOSS community he is. I’ll be having a meeting with them tomorrow afternoon to discuss this topic and I’ll learn more about that from him.

This topic was brought up at last week’s county commission meeting briefly and I was in attendance and thought there might be a FOSS solution that works on the enterprise level.

I was kind of wondering to myself this morning what the folks at IBM and Red Hat use for their corporate email system. Does anyone have an idea what that might be?

Tom, thanks for the Zimbra link, I’ll give it a look now.


Late to the party and I’m sure you’ve probably already beaten your head against the wall arguing, but the “never-ending fees” pay for uptime, security and powerful anti-spam capabilities. I love FOSS solutions, but I never delude myself that it is truly free, particularly for something as complex and vulnerable as a complete collaboration solution (email begets calendaring, etc). The administrator will be paying a subscription for a professional solution or in staff replicating and maintaining said features. Worst case, they’ll be paying with their job if the homegrown system is compromised.


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Yep, your absolutely correct. I explained all of that to him, too. One has to pay regardless. I mentioned that if we do our own thing, we have to babysit it, watch the spam filters, keep the hardware running, replace the hardware, protect the security of it all and so on.

At this point, they are going to do a pilot program of a self-hosted, self-managed solution, probably running Apache and see how it goes. If it doesn’t work out well and to their satisfaction, then O365 is probably the way they will go.

@SandboxGeneral - from my experience with IBM they Use Domino/Notes inhouse - globally - and have done so for the last 20 years at least - it’s a phenomenal platform, but pricey …

Personally I use GSuite, but for business we use Office 365 … it just works … most of my clients are either migrated to Office 365 already, are are planning the move from either IBM Domino/Notes or Exchange to Office 365 … still have the odd one that refuses to let their data go to the cloud, and for that they have their own fault tolerant Exchange servers on premise … varied solutions, but they all work.

For free solutions, there are loads, a good one that I found years ago and installed in some schools was MailEnable [https://www.mailenable.com/standard_edition.asp] - I’d be interested to hear what @LTS_Tom has to say on that product.

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I recently installed Zimbra VM on Proxmox server in a lab environment to test the UI and practicality at production scale…it seems to be good so far and Zimbra Zimlets are a nice add-ons with chat and calender support.

The community edition is free to use it has the built in antivirus and Anti spam. To secure the mail server I have put it behind Proxmox Mail Gateway VM another cool opensource email security from proxmox and seems goo so far…

currently being used on intranet (LAN) and need to configure for wild.

I hope to use googlemail servers to route the email…so you are not spammed (I need this configuring)

hope this helps someone to play with


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I have a dream of deploying UCS (Univention Corporate Server) at work for a future customer, in the future. See it has a nice management for different open source components, as well as framework for plugins/addons and container-apps. I think Zimbra is in there somewhere, it also has Active Directory support and all that.

Might fit well in a municipality.

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UCS seems like an on premise cloud type (like SaaS). Just looked at the zimbra app on UCS— this app just connects to the Zimbra installation locally on a different sevrer. UCS just provides the Active Directory service (Unidirectionally) that all.

Thanks for bringing it up…UCS needs some digging in the lab

you will still need to install zimbra seperately

Ah yeah. Forgot to double check what Zimbra-feature it has, but ok, it connects to a different server with zimbra.

Well, if one doesnt want to run windows AD, one can then run UCS AD instead

I personally just use the DNS-management in UCS to handle my records, a bit heavy perhaps but works great.