Top 6 open source desktop email clients

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A pile of paper mail

Judith E. Bell. Modified by CC BY-SA 2.0.

This article was originally published on October 8, 2015, and has been updated to reflect new information and project changes.

Mobile and web technologies still haven't made the desktop obsolete, and despite some regular claims to the contrary, desktop clients don't seem to be going away anytime soon.

And with good reason. For many, the preference for a native application (and corresponding native performance), easy offline use, a vast array of plugins, and meeting security needs will long outweigh pressures to switch to a webmail email client. Whether you're sticking with a desktop email client because of a corporate mandate or just personal preference, there are still many great options to choose from. And just because you may be stuck on Windows doesn't mean Outlook is your only option; many open source clients are cross-platform.

In this roundup, we take a quick look at six open source options for desktop email, share a little bit about each, and provide you with some options you may want to try yourself.


For many years, Mozilla Thunderbird was the king of the open source email clients. It was available on all major platforms, and it had great success alongside Mozilla's now-flagship project, Firefox. Thunderbird has been around for over a decade and was immediately popular from the start, receiving over a million downloads in its first 10 days of public release.

In recent years, the thunder behind Thunderbird got a little quieter, and in mid-2017 the project announced it would move off Mozilla's infrastructure, but keep the Mozilla Foundation as its legal and fiscal home. Several new hires were made to advance the project, with plans to bring in new developers to fix lingering issues and transform the codebase to be based on web technologies.

Thunderbird is full-featured, with a number of well-supported plugins adding everything from calendar support to advanced address book integration, and many specialized features including theming and large file management. Out of the box, it supports POP and IMAP email syncing, spam filtering, and many other features you would expect, and it works flawlessly across Windows, macOS, and Linux.

Thunderbird is made available under the Mozilla Public License.


Claws Mail

Claws Mail, a fork of Sylpheed, is a fast and flexible alternative that might be appealing to anyone concerned about performance and minimal resource usage. It's a good option, for example, if you're working within the limited processing and memory capacity of a Raspberry Pi, for example.

But even for those with virtually unlimited computing resources to throw at a mail client, Claws Mail might be a good option. It's flexible, probably more so than Thunderbird or some of the other options in this list, and it has a number of plugins available for those who want to extend it. And it prides itself on being fast and reliable, too, in addition to sporting a simple interface that's perhaps ideal for new users.

Claws Mail is based on the GTK+ framework and made available under the GPL.


Claws email


If you're a user of the popular Fedora or Debian distributions, you're probably already familiar with the next option on our list, Evolution. Evolution is an official part of the GNOME project, but it didn't start out that way. Originally developed at Ximian, and later Novell, Evolution was designed from the ground up to be an enterprise-ready email application.

To this end, Evolution supports Exchange Server and a number of other email setups you might find in a corporate environment. It's also a full personal information manager (PIM), sporting a calendar, task list, contact manager, and note taking application, in addition to handling your email. Even if it's not the default mail application in your distribution, you might want to take a look if you're interested in these features or the included spam filtering, GNU Privacy Guard (GPG) support, integration with LibreOffice, or a slew of other features.

Evolution is made available as open source under the LGPL.




Geary is a project originally developed by Yorba Foundation, which made a number of different GNOME software tools. Geary supports a number of popular webmail services as the mail backend through IMAP.

Geary doesn't have a lot of features compared to some other clients on this list, but its simple interface might be appealing to users frustrated with unnecessary complexity in other email programs. Geary is available under the LGPL.




KMail is the mail component of Kontact, the personal information manager included with KDE. KMail supports a variety of email protocols, including IMAP, SMTP, and POP3, and through its integration with the other Kontact components, it could be considered a complete groupware suite. Despite its Linux routes, a Windows build is also available.

With its long history, KMail has developed most of the features you would expect to find in a modern mail program. While it fits nicely into the KDE group of applications, some may find its interface clunky compared to others. But give it a try and see what you think.

KMail is made available under the GPL.




Mailspring, the new kid on the block, is a relaunch of the now-defunct Nylas Mail by one of the original authors. It replaces Nylas' JavaScript sync engine with a C++ core, which is said to minimize the application's RAM and power demands, and removes heavy dependencies to add speed. Its features include a unified inbox, support for IMAP (but not ActiveSync), Gmail-style search, themes, and message translation.

Mailspring is available for macOS, Windows, and Linux, and it's licensed under GPLv3.


Of course, there are many more options above and beyond these, including the full-featured PIM Zimbra Desktop or one of the lightweight alternatives like GNUMail that might be the best choice for your situation. What's your favorite open source desktop email client? And with webmail as the first choice of many users, what do you see as the role of the desktop email client in the years to come? Let us know in the comments below.

Jason Baker
Former Red Hatter. Now a consultant and aspiring entrepreneur. Map nerd, maker, and enthusiastic installer of open source desktop and self-hosted software.


You missed sylpheed.

Thanks, Claws Mail in the list above is a fork of Sylpheed; I'm not overly familiar with the original. What would you say its main selling points are?

In reply to by Goksin Akdeniz (not verified)

This article was dull in 2015.
Post-Drumph Techtalk or just lazy?

In reply to by Goksin Akdeniz (not verified)

Thanks for reading, Ben. We update the "evergreen" content on this site from time-to-time because many readers end up on these pages via search engines. I know this topic isn't of interest to a lot of people (for example, I only use a web mail client), so if there's something else you're interested in, we publish 3-5 articles a day.

In reply to by Ben Nevis

How is the Exchange support in Evolution these days? It's been a few years since I've had to use it, but I recall it being rather unstable.

Fortunately it's been a few years since I've had to use Exchange, so the extent of my endorsement on that end is "it worked that one time I set it up several years ago."

In reply to by bcotton

run exchange 2013 here and ubuntu 14.10 with evolution worked fine. initial sync took some time but none of the old ews issues it used to have, worked fine for me.
actually right now working on installing i on kububtu 15.10 as its one of the few clients that work well with exchange w/o paying for plugins like thunderbird

In reply to by bcotton

I like Thunderbird (or Icedove in Debian) very much. The customization is a major plus with this client.

You ought to look at geary too.

Thanks, Geary is actually #4 on this list. And in full disclosure, one of the former lead devs of Geary is a good friend of mine from middle school who may very well have been the first person to show me Linux, probably 15 years ago.

In reply to by SimonJ22 (not verified)

N1 saves emails on their own server. How can you recommend such a client which compromises privacy???

Apparently the server is hosted on your own machine. I don't really see the appeal.

In reply to by Justin (not verified)

Thanks for this interesting overview.
I (as non-IT technician) like Zarafa as email client. I am curious if you know this open source product and if so is there a reason why you did not mention it in this Top 5?
Looking forward to your reply.

Hi Emiel, I looked into Zarafa just a little bit. The authors say it is based on open source technology, but I couldn't find a link to the source code anywhere. Do you happen to know where this is made available?

Meanwhile, this list is limited to strictly desktop clients; we did a roundup of webmail clients a few weeks ago which you might be interested in:

In reply to by EmielBrok

The thing I like the most about Thunderbird is that by default it automatically blocks remote content in messages, so the person (or a company) that's sending you an email does not know whether or not have you read the email until you decide to allow remote content. This stops senders from using web beacons ( to track its readers.

How many Open Source e-mail clients are there?
I count mail, mailx, alpine, elm, and mutt.

You did not mention Zimbra Desktop, which is open source.

Excellent article, Jason. Great list, and neatly explained too. Thanks, Niraj (Founder at

I'm surprised mutt hasn't been mentioned thus far. I love mutt. It works with a wide variety of scenarios. I have used it in a unix environment, Windows exchange, and recently O365 environment. Sometimes a GUI just gets in the way. :)

You should discuss stability and performance in addition to features. I've had issues with both stability and performance in Evolution, but I run multiple I map connections and multiple calendars.

With the same configuration, Thunderbird is more stable but the password management is subpar - I have to enter my keychain password 5 times at startup for the account passwords to apply for all accounts and calendars.

I have yet to find a mail client on Linux with a good user experience for complex setups

Thunderbird, with the calendar extension, is probably the closest to the Outlook layout. I haven't used it in a while but may be setting it up sometime soon, otherwise I usually end up using Geary or the web browser.

I ran Thunderbird with Office 365 at my last job with no problems. Both email and calendar worked fine.

After reading this, I decided to install Mailspring and see how that does. So far, so good. Windows10. Thanks.

Thunderbird linux does not know junk mail from manure!

My major concern is that Thunderbird may die out, despite it being highly popular, because they simply don't have the staff/resources needed to keep the client viable for the future (bug/vulnerability fixes, API changes at the server end, loss of API support in the tools to build the application, etc). And as the client falls behind, add-ons will probably die and become obsoleted by the same sort of API changes as well.

So I've been looking around for possible replacement options. I want something that can support multiple email accounts (at this point they're all IMAP), keep my archived mail (old POP3 versions of a couple of those other IMAP accounts), plus calendar (sync to Gmail, and maybe Cozi as well), decent address book capability (I'm syncing to my Google Contacts these days). And I want local offline sync of those IMAP accounts.

Would also like to use it for mail *AND* calendaring for my Gmail-hosted work email. I had tried it with the current released versions of TBird and Lightning (along with the Google Provider add-on), but it has a severe bug (already known and not anywhere close to being fixed) that it tries to notify you of all past as well as current calendar entries, and the notifications can't be cleared.

Thunderbird is still one of the favorites, because of the integration with Enigmail (human interface for GnuPG).

Thanks for the update on that interesting article. For me e-mail clients are still extremely relevant and at the core of my daily workflow. When Mozilla announced they would not develop Thunderbird further I switched to Evolution and I am pretty happy with that all in one solution of e-mail, calender and tasks. Works fine for me, though I might check out Geary, Mailspring or some other lightweight client for my private accounts in the future.

I would use Claws Mail if it would sync its iCal plugin with Google calendar. Evolution is nice but its RSS plugin is buggy and very slow to fire up and slow to load emails.

T-bird causes gmail to tell me I'm using a 'less secure app or device'. They say t-bird and outlook are less secure. What is a more secure desktop email client that I can use. I definitely do not want to be forced to go online to do my emailing; ac

I've been using Thunderbird for as long as I can remember, and it has never let me down. I have email accounts galore (GMail, Yahoo....TWICE,, and AOL) And it performs regardless of which version of Linux I happen to be on. I'm glad that this project never died out! I've tried Evolution and a few others, but to me Thunderbird gets the job done with the perfect amount of style and customization.

As for the state of the desktop? I have never subscribed to the notion that desktops computing will "go away" There are way too many manufacturers of components and complete built systems for this to die. There are too many people who have desktops that they've labored over relentlessly to get it "just right" in regards to look, power, components, etc. As far as I see? desktop computing will NEVER go away, a lot of the older generation won't ever feel comfortable saving their documents, movies, pictures and other personal data in the cloud, and its here where desktops computers will forever reign. You can have a tower with three bays filled with three 8TB hard disks to save all your data while running the Linux distro of your choice from a 250GB ssd....while making sure your Radeon / Nvidia video card sits snugly in its socket, and whenever you're ready? you can increase the size of your RAM from 64GB (permitting your system can handle it!) So nope PC's are here to stay. Think of it like this: they can improve the a sporting events etc...but there will FOREVER be lighting for mankind, because there's nothing that can replace its ease of use and convenience.....the same can be said of PC computers, in America?...almost every household has one. Even if its just sitting in the attic collecting dust?'s THERE. Because its just something mankind has grown to have a need / use case for in almost any situation.

Mailspring looked interesting, so I had a go at it. Then I discovered that those Mailspring clowns force you to create an account with them before you can even set up you email client. So I gave them a big middle finger and removed it from my system.

After having too much trouble transferring all my mail accounts and settings from Windows to Linux, I was looking for an alternative.
In my opinion Thunderbird is getting worse and worse!
Claws Mail makes a good impression, but already after the first start and the attempt to set up only ONE mail account, was the exclusion of Claws Mail. You can't set up a separate IMAP/SMTP login for a mail account in Claws Mail (two different servers, two different users). So Claws was useless for me.
Evolution is too overloaded for a simple mail client with filter functions.
KMail fails because I don't use KDE.
Mailspring is not found in the Ubuntu repository.
Geary is too limited with its functions.
So, no more alternatives? Already sad for Linux...

Been using Thunderbird with Lightning (calendar) to connect to our internal Zimbra server for over a decade. Lately, Mozilla has gone crazy with their certificate validation and made Thunderbird useless for us.

Webmail is a toy to me. The only time I use it is when there's no other choice. A full email client is so much more efficient once you have the keyboard shortcuts down. Every time I have to move a hand to the mouse, that's lost productivity.

Ended up installing Claws-Mail today. I'd used it previously for a few weeks, but Thunderbird was a little nicer. Hooked up my few accounts in Claws to the Zimbra Accounts (which also federates external mail accounts from a few other places), saw one complaint about the internal cert, told it to accept and moved on. That's what Thunderbird should have done.

We have an email gateway for the outside world that all SMTP goes through. That box has the real certs. Zimbra isn't on the internet and can only be accessed by our people when they run our VPN.

Anyways, thanks for this article. I was vaguely remembering alpine and K9-Mail as options. Seems K9 is for phones.

Back when I was using a single back end server to receive Email, I was using Email clients to import and read and retain or remove messages from several sources, including Yahoo Mail and Gmail.

One of my favorite mail formats was the Rand MH format, as opposed to the UNIX mbox format. When I used a UNIX workstation I had message filters set up to remove junk mail and store specific content in particular folders.

Thought I'd try Mailspring --- first thing it wanted was for me to create a mailstring account --- don't see why I need that to read mail from my own servers.

Goodbye Mailspring - alas I never got to know you!

I used to use the old integrated Netscape with a mail client and a browser. Later, when Seamonkey replaced Netscape, I used Seamonkey Mail.
I've also used Thunderbird Mail. All three were quite effective when using local mail client software.

Over the years, however, I used a lot of different computers, both in hardware and software. Though with IMAP I could access some of the same content, the near ubiquitous availability of Webmail with reliable Internet access greatly diminished my need for Thunderbird or anything else.

I'd say that Claws was probably quicker than Netscape, Seamonkey or Thunderbird, but the Mozilla family of Email clients had rich functionality and worked across all platforms, proprietary, freely available, or "Open Source".

Nevertheless, it has now been a few years since I've even used an Email client, Outlook or otherwise with a client on a local system. Yahoo Mail and Google Gmail have both proven to be exceptionally reliable and also capable of filtering or at least identifying messages I want to isolate or remove.

I don't see how the Yahoo client is considered reliable. In the discussions on email clients, I find myself a lightweight user with lack of experience, yet even I can't imagine doing in Yahoo what I do in Thunderbird. First, of course, is the problem of unconsolidated clients for multiple accounts. Second, though, is that Yahoo is a mess. The page is cluttered and has little functionality. Can you easily manage 30 filters for your mail? Can you easily manage tags on mails? Can you easily read your email in the diminutive space Yahoo provides you? How about the advertising they show in the Inbox? Sorry, that's annoying, not helpful. I am also upset with the degree to which Yahoo intrudes on privacy. They read every email and keep that data for marketing purposes. Obviously, do what you like, but for the life of me I can't imagine how their "client" is considered anything but an advertising platform designed to optimize customer control.

In reply to by Brian W Masinick (not verified)

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