The 5 best alternatives to Thunderbird
Thunderbird has established itself as the go-to open-source email client, valued for being free and independent.
Its 4.4/5 rating on Capterra confirms how attached its users are. The friction lies elsewhere.
It stems first from an interface seen as dated and from add-ons that need monitoring. It also stems from support rated 3.7/5 and from the lack of both a mailbox and collaboration tools.
For an SME, an IT department or a local authority, these issues weigh on day-to-day work as well as on data sovereignty.
This comparison reviews five serious alternatives, with a deliberate focus on open-source and French solutions. Leading the ranking is Wimi, the French sovereign collaborative solution that hosts your email in France.
Wimi: the sovereign French collaborative suite
Choosing Thunderbird already means choosing digital independence on the software side. Wimi extends that choice all the way to the mailbox itself, with business email hosted in France on your own domain names.
Your messages stay in mainland France, outside the reach of the Cloud Act and FISA, with a French vendor founded in 2010.
Nothing forces you to leave Thunderbird overnight. Wimi Mail works over IMAP and SMTP, so it runs in Thunderbird, Outlook or Apple Mail: your teams keep their software during the transition, then adopt the Wimi interface at their own pace.
Where Thunderbird grows through add-ons, Wimi builds the features natively into the inbox. You turn an email into a task, save an attachment to the Drive or create an AirTime video meeting, with no extension to install or monitor.
The shared calendar is part of the same suite, alongside the Drive, Chat and video conferencing.
To save time, the AI assistant Wimi Neo takes care of summarizing long emails, correcting spelling and rephrasing a message. On smartphones, your teams find their inbox in the Wimi Inbox app, available on iOS and Android.
Security rests on the SecNumCloud SaaS 3.2 qualification, obtained from ANSSI on May 18, 2026: it is the most demanding qualification in France. Wimi is also ISO/IEC 27001:2022 certified and GDPR compliant, with no data transferred outside the European Union.
On satisfaction, Wimi scores 4.7/5 on Capterra, Appvizer and GetApp, and the Palace of Versailles is among its clients.
Who is it for? Organizations that want to bring email, calendar, files and tasks together in a sovereign environment, without piling up modules to maintain. Longtime Thunderbird users get a gradual transition, since their software remains compatible.
Betterbird
Betterbird is an enhanced version of Thunderbird that is free and adds features and exclusive fixes.
It offers, for example, a multi-line view of the message list, vertical tabs, per-account colors and regular expression search. The project is led by Jörg Knobloch, a former Thunderbird developer.
Its practical advantage: Betterbird installs alongside Thunderbird, on the same profile. You can therefore try it with your usual accounts and folders, then roll back if needed.
The software runs on Windows (including a portable version), macOS and Linux, and is funded by donations and a shop.
Betterbird follows the same logic as Thunderbird: it is an email client, not a mailbox. It provides neither message hosting nor team tools, such as a shared calendar or online file storage.
Who is it for? Thunderbird users who are happy with it but want more comfort day to day, without changing their habits. They keep their profile, their accounts and their email provider.
Mailo
Mailo is a French email service, run by a company incorporated under French law, that stores data on servers in France. Unlike Betterbird, Evolution or Mailspring, Mailo does not replace your software: it provides the mailbox itself.
The service combines webmail, a calendar and storage space for documents and photos.
iOS and Android apps are available, and IMAP access lets you read your Mailo inbox in Thunderbird. You thus switch hosts while keeping your usual client.
Mailo offers three plans: Free (with banner ads), Premium and Pro. The Pro plan adds custom domain names and pooled storage, two features professional organizations expect.
Who is it for? Individuals and small organizations that want a simple French mailbox, to use with Thunderbird or through webmail. It is the most direct option for switching hosts without switching software.
Evolution
Evolution is an open-source client from the GNOME project that brings email, calendar and address book together in a single application. The three functions share the same interface, which saves you from juggling several tools.
The software ships with the major Linux distributions, including Fedora, Linux Mint and Ubuntu, and is also available as a Flatpak package. An optional component, evolution-ews, connects it to Microsoft Exchange servers, a useful point for organizations still running on Microsoft infrastructure.
Evolution is built for Linux: on Windows or macOS, Betterbird and Mailspring will better meet the need. Like Thunderbird, it remains a client, and the hosting of your messages depends on the provider you use.
Who is it for? Linux users who want an integrated client, especially when working with an Exchange server. Those working on the GNOME desktop also get a tool developed by the same project.
Mailspring
Mailspring is a desktop client for Mac, Windows and Linux whose code is open under the MIT license. It is published by Foundry376, LLC.
Mailspring supports IMAP and Office 365 accounts, with a unified inbox, advanced search and grammar checking. The software comes in a free version and a paid Pro plan, which adds read receipts, link tracking, scheduled sending and message templates.
There are two limitations to know about before adopting it.
The full calendar has been announced but is not yet available, with the site saying "coming later this year". The site does not mention a mobile app either.
Who is it for? Those who want a modern interface on desktop, whatever their operating system. This choice mainly suits email-centric use, with no immediate need for a collaborative calendar.
How to choose your Thunderbird alternative?
Before comparing features, ask yourself what really bothers you about Thunderbird. The answer almost always points to the right choice.
- If it's the interface, keep the same logic with more comfort: Betterbird on Windows, macOS and Linux; Evolution on Linux; Mailspring for a more modern look.
- If it's the hosting, change your mailbox: Mailo for simple use, Wimi for an organization.
- If it's teamwork, a client won't be enough: a shared calendar, files and video calls call for a collaborative office suite.
Keep one last reflex: check where your messages are stored. It is the host, not the software, that determines the law that applies to your data.
And nothing stops you from continuing to use Thunderbird to read a mailbox hosted in France.
Why switch from Thunderbird to Wimi?
Three complaints come up often in user reviews. The first is about usability: "Not very intuitive to use," sums up one user on Capterra France in January 2025.
Wimi designs its app together with the rest of the suite, and its CEO, Lionel Roux, puts it simply: "What good is an ultra-secure sovereign system if it is almost unusable?"
The second concerns support, rated 3.7/5 on Capterra: in September 2025, one user said they found no way to reach Thunderbird while their outgoing emails were blocked. At Wimi, key features are native, with no add-on to monitor, and a team supports your migration.
The third is less obvious: Thunderbird remains a client, so your emails sit with another host. Wimi keeps them in France, under the SecNumCloud SaaS 3.2 qualification, with the calendar, the collaborative drive and video calls in the same place.
Looking to replace Mailbird or Outlook too? The reasoning is the same, as our selection of Outlook alternatives shows.
The simplest option is to try it: set up Wimi Mail in Thunderbird and see for yourself.
FAQ
Is Thunderbird still free?
Yes. The official Thunderbird website describes it as "Free, forever," and the project, part of the Mozilla family, is funded by donations from its users.
The Thunderbird Pro services (Thundermail, Appointment and Send) are offered separately and are still in beta at this time.
Can you use Wimi Mail in Thunderbird?
Yes. Just add your Wimi account to Thunderbird over IMAP and SMTP, like any business mailbox.
You get hosting in France without changing software, then move to Wimi Inbox or the Wimi interface when your teams are ready.
Does Thunderbird support Microsoft Exchange?
Partly: Exchange email has been supported natively since version 145. The official roadmap, updated on July 23, 2026, still lists finishing the Exchange protocol, calendar and address book included, as "Active".
If your organization is instead looking to replace Microsoft Exchange, our dedicated guide compares server-side solutions.
Is Thunderbird available on mobile?
Yes, but only on Android for now. The official mobile page offers an Android app, available on Google Play and F-Droid.
However, it does not mention any iPhone app.
How do you migrate your emails from Thunderbird?
It all depends on the account type. An IMAP account keeps your messages on the server, whereas local folders stored on the computer must be exported before the switch.
To switch hosts as well, Wimi offers a guided migration of your mailboxes. You can keep reading Wimi Mail in Thunderbird throughout the transition.
