Four open source email clients worth checking out

Open source email clients have many advantages over proprietary software, but choosing the best option can be challenging. Discover our top picks.
In light of numerous privacy concerns connected to Big Tech platforms, people started being more careful about the software they use for daily activities. Email is an unavoidable part of almost every workflow, so your chosen provider and client can make a world of difference to the levels of security and privacy you can enjoy.Open source email clients give more control to users than traditional platforms, so they’re an excellent choice if you care about data ownership. This guide will explain why choosing them over proprietary software is a good idea, and then you’ll see concise reviews of four clients so that you can pick the one that suits your needs.
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Benefits of using an open source email client

When you go with a typical Big Tech email client, what you see isn’t necessarily what you get. Unless you closely examine the platform’s privacy policy and data practices, it’s hard to know what happens in the background and how your sensitive information is managed.Open source platforms fix this issue by letting every user inspect the source code. There are three major advantages of such options:
  1. Complete transparency
  2. Greater security
  3. Excellent value for money

Why transparency in an email client matters

Open source email clients make their codebase publicly available, ensuring there are no secrets. Even though you may not be able to inspect the code yourself if you’re not a tech buff, you can trust that other users have validated the platform.Such transparency has many benefits, most notably lower risk of vendor lock-in. When you know precisely what to expect from a client, you can make an informed decision without encountering unpleasant surprises once you’ve already committed to it.

How open source platforms ensure security

With proprietary software, security issues are handled behind the curtain. If you notice any, you need to wait until the patch comes out to fix it. Users have no influence beyond providing feedback, which can take a while to implement.This isn’t the case with open source platforms because independent developers have full access to the code. They can review it and resolve any red flags proactively. The result is a more secure, bug-free solution that guarantees a quicker response to safety issues.

What makes open source email software cost-effective

Many open source email clients are free to use, and the paid ones typically come at a fair cost. As any developer can voluntarily contribute to the product, launching and maintaining it is cheaper than a proprietary solution.Besides, most open source software providers aren’t focused on the bottom line as much as Big Tech companies. The goal is to create a solid product, which can be achieved more easily with the community’s support.

Best open source email client—pros and cons of four popular options

Numerous open source email clients have surfaced over the years, but four solutions stand out:
  1. Mozilla Thunderbird
  2. Claws Mail
  3. Zimbra
  4. Skiff Mail

Mozilla Thunderbird

Source: ThunderbirdWith over 20 million users, Mozilla Thunderbird is easily among the most popular open source email clients on the market. Its widespread use stems from extensive functionality and user-friendliness, but the platform suffers from a few notable drawbacks making it a subpar option for certain user categories.

Pros and cons

Thunderbird is free to use, which is among the main reasons for its massive adoption. No features are hidden behind a paywall, so you can explore its full potential at no cost. If you end up enjoying it enough to contribute, you can make an optional donation.The client supports three email service providers (ESPs):While the combined user base of these ESPs is large enough to give Thunderbird a wide audience, the client is still a bit exclusive. Unless you use any of the above providers, you’ll either have to migrate to one or start from scratch with a new account.On the bright side, you can add unlimited email addresses to Thunderbird, so managing multiple accounts should be straightforward.The platform’s standout feature—tabbed email—was inspired by Firefox, Mozilla’s famous browser. It lets you open emails in new tabs to manage them more easily, which is a handy option you can’t find in most clients.If you’re a privacy-conscious user, Thunderbird might not be your best choice. By default, it doesn’t support end-to-end encryption (E2EE)the gold standard of email security, ensuring nobody but the recipient can access your emails. Thunderbird requires users to manually configure the private encryption key and enable E2EE, which can be complex and time-consuming.
Made by a reputable companyOnly supports three email providers
Free to useDoesn’t offer end-to-end encryption by default
Supports tabbed email.

Claws Mail

Source: Claws MailClaws Mail is a lightweight client focused on customizability. It’s packed with useful features that make it suitable for advanced users, but they come at the cost of user interface and overall simplicity.
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Pros and cons

If you need to manage numerous inboxes and stay on top of your correspondence, Claws Mail can be a solid option. You can use it with any provider and leverage its many features to keep your inbox clean.One such feature is advanced filtering, which lets you create custom filters based on the sender, phrases, flag colors, and many other factors and their combinations. You can personalize your inbox to manage it more effortlessly.Claws Mail supports many plugins, including strong threat-scanning add-ons. There are also plugins for various E2EE protocols like S/MIME and PGP/Inline, which can safeguard your correspondence to an extent. The only issue with these protocols is that they’re outdated, so you still won’t get top-of-the-line E2EE.Another major disadvantage of Claws Mail is its user interface, which is far from sleek. The old-school style will likely bother design-focused users and damage their overall experience.The initial setup matches the overall outdated feel, as it requires quite some manual work. There’s no automatic setup, even for the most common providers, so getting started might be laborious and complex for new users.
Fast and lightweightOutdated interface
Custom filtersNo automatic setup
Numerous plugins.


Source: ZimbraZimbra is a collaboration suite primarily aimed at business users, though it’s also suitable for personal use thanks to its simplicity and user-friendliness. It suffers from operating system constraints and similar design issues as many of its competitors, but it can be a decent choice if you look beyond aesthetics.

Pros and cons

Zimbra is used by numerous businesses across the globe and offers cloud-based, on-premises, and hybrid deployment. The platform’s Network Edition offers a comprehensive suite of collaboration tools, while the Open Source Edition is stripped-back and features the basics that most users should find useful enough.The Open Source Edition is free to use, but it’s exclusive to Linux distributions:
  • Red Hat Enterprise
  • Oracle Linux
  • Ubuntu
  • CentOS
  • Rocky Linux
To use Zimbra on Windows or Mac devices, you’ll need to buy the Network Edition. Zimbra doesn’t offer pricing information on the website, so you’ll need to get a quote.You can use any IMAP/POP3-supported email provider with Zimbra and create as many accounts as you want. The interface is a bit outdated but clean and easy to navigate, so new users shouldn’t have trouble with it.A handy feature setting this platform apart is HTML formatting, which gives you more email customization options than a standard email text editor.Besides limited platform support, the Open Source Edition has poor mobile integration, so you might miss important emails while you’re away from your computer.
Clean interfaceExclusive to Linux
Free to usePoor mobile integration
HTML formatting.

Skiff Mail

Source: Skiff MailSkiff Mail is a privacy-first email service using advanced end-to-end encryption to ensure complete security and give users full ownership of their data. It pairs strong security measures with a user-friendly interface to make privacy available to every user regardless of their tech skills.

Pros and cons

Skiff Mail is more than an email client—it’s a comprehensive solution letting you send and manage emails without privacy concerns. While you need a Skiff account to use the platform, creating one comes with many benefits.When you create a Skiff account, you can rest assured your correspondence is safe from prying eyes and cyberattacks. The platform uses end-to-end encryption to safeguard your emails and attachments with two keys:
  • A public key used for sending encrypted emails
  • A private key for decrypting messages
Emails are encrypted on your device before leaving it, so nobody—including Skiff’s team—can see their contents.Skiff Mail uses zero-knowledge login, which means your credentials aren’t stored on the platform’s servers. Your account and everything in it remains completely confidential.You can learn more about Skiff’s security measures and other features by reading the whitepaper. If you want to inspect Skiff’s codebase, you can find all libraries on the platform’s GitHub.Besides transparency and privacy, Skiff Mail offers numerous features:You get all of the above for free, but you can choose between three paid tiers if you need to scale your workflow:
  1. Essential—From $3/month
  2. Pro—From $8/month
  3. Business—From $12/month
Advanced E2EE ensuring complete confidentialityRequires a Skiff account
Zero-knowledge login.
User-friendly interface.

Get started with Skiff Mail

Signing up for Skiff Mail is easy, and you don’t need to leave any personal information to get started—all you have to do is:
  1. Visit the signup page
  2. Choose your account name and password
  3. Explore Skiff Mail
Your free Skiff account gives you access to three additional end-to-end encrypted platforms:If you want to enjoy complete privacy but don’t want to lose your past conversations, you can take advantage of Skiff’s one-click migration. The platform won’t save unencrypted email copies, so your correspondence will be secure from the moment you transition.

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