Top 7 Exchange Server Alternatives (Free & Open Source)

  

Written By Tej Pratap Shukla

Approved By Anuraag Singh

Modified On January 7th, 2026

Reading Time 6 Min Read

We review the top open-source Exchange Server alternative and bring you the best replacement options available in 2026.

MS Exchange has, without a doubt been the default choice for any organization. However, when we zoom out and look at the Exchange Server versions, a trend emerges: both cost and complexity seem to go up.

With Exchange 2016 and 2019 both in EOL, it seems just the right time to change to a different platform. To help you decide, I have listed all the top alternatives to choose from.

See All Replacements for Exchange Server At a Glance

If you want to switch over to eliminate licensing costs incurred with the release of Exchange Server SE, the following options work well. However, you need to have personnel with core technical skills to maintain the server.

If you prefer a more managed solution, you have two excellent options.

Now, let me go over the replacements in more detail.

Top 5 Free & Open Source Exchange Server Alternatives

1. Grommunio (The “Drop-In” Replacement)

If you want to do away with Exchange but still want Outlook Client compatibility, Grommunio works best thanks to its native MAPI compatibility. The best part of choosing it is its drop-in nature, meaning you can point your Outlook clients to this Linux server and neither the user nor the software will know the difference.

2. Zimbra Collaboration (Open Source Edition)

Zimbra has been a competitor of Exchange Server since the early Windows vs Linux days. It comes with an intuitive Webmail portal that gives OWA a run for its money.

3. Mailcow (The Docker Suite Style Exchange Server Alternative)

Designed for admins who love a Docker-like container setup over traditional mailbox architecture. It bundles Postfix, Dovecot, and SOGo together.

4. Carbonio CE (Puts Privacy First):

Companies for whom privacy is of utmost importance, more so than fancy UI elements, should choose Carbonio. Zextras built it to focus on privacy and comply with the strict laws like GDPR.

5. iRedMail (For those who want control):

iRedMail is known for the sheer amount of control it allows its users. Admins can use shell scripts to install their favorite server component, like Postfix, Dovecot, etc directly on their Linux distro. Transparent self-managed server leaves you in charge of what to keep and what to remove.

Best Cloud-Based Exchange Server Alternative

Office 365 is the go-to platform for any organization that wishes to ditch the hardware management costs associated with an on-prem system like Exchange.

Not only that, but the sheer amount of business suit apps that you get is a tremendous ROI, provided that you require and use them.

Another major advantage of O365 is that you can maintain a hybrid setup where you get the privacy of on-premises and the flexibility of the cloud.

This is only possible because both Exchange and O365 come under Microsoft’s umbrella.

Move to cloud ASAP with the one and only Exchange On-Premises to O365 Migrator by SysTools. A free demo is available right now to bring Exchange Server data elements to the cloud.

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Office 365 is a great option, and you can compare all Office 365 plans to select the one that works for you. Get a rough idea on how long email migration takes before hand.

Cons: If you are not willing to enter a perpetual subscription cycle where you have to pay for every new license, then M365 cloud is not for you.

Top MS Exchange Replacement for On-Premises

HCL Domino allows organizations to prioritize security, and at the same time, develop custom apps that work on both Windows and Linux.

However, the biggest win of HCL over Exchange is the storage space efficiency. HCL has built the Domino Attachment and Object Service (DAOS) technology that can save up to 90% disk space. It does it by performing a deduplication on the email attachment server-wide and linking them via pointers.

Switch to the best Exchange On-Premises alternative with SysTools Exchange to HCL Domino Migrator. This software eliminates the file format transformation and does a direct server-to-server transition in real-time.

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Download the demo today to bring all emails, contacts, and calendars of every Exchange Server user account into HCL.

Cons: Organizations may have to hire additional staff or train existing ones to use Domino Server and related components.

Our Verdict

Looking at all the points I have put forth, one thing is for sure: there is no single best Exchange Server alternative that works for everyone. However, at the same time, many of the options that I gave you work well in niche situations. It is up to you, the IT admin, and all other stakeholders to decide by evaluating both the current circumstances and the future plans.

In my opinion, the free and open source replacements work well for those who have a team that understands the tech and is willing to invest more time or has a tight budget.

If you prefer the Exchange Environment but want to eliminate hardware management, then Microsoft Office 365 is the place to be.

Additionally, if your industry has a strict compliance rule that mandates the data to stay on-premises, but Exchange Server is too overbloated, then HCL Domino is a great option.

At the end, choosing a platform is just the beginning. The real challenge is migrating your entire digital infrastructure. So choosing the right partner is non-negotiable. You need not waste time finding a solution provider; the options I have listed are the best in business.

Most Asked Queries on Exchange Server Alternatives

Q: Which is the most affordable replacement for Exchange Server?

If you have a zero-dollar budget for software, iRedMail or Mailcow are the best free self-hosted options.

Q: What happens to Active Directory after I replace Exchange Server?

You can keep it, but lose the ability to manage some email attributes.