Ubuntu Kylin is an interesting case in the Linux world because it sits in the Ubuntu family, yet it is clearly aimed at a Chinese-speaking desktop audience and ships with its own polished desktop flavour, usually on top of UKUI. That matters when choosing an email client. On Ubuntu Kylin, you are generally looking for software that behaves well on a Debian-based system, installs cleanly via APT, and feels comfortable on a desktop that favours simplicity, a familiar tray experience, and a fairly conventional workflow rather than a heavily customised power-user environment.

In practical terms, Ubuntu Kylin users are often best served by clients that are stable, easy to package, and not too fussy about desktop integration. Because the distro is Ubuntu-based, deb support is the most natural fit. Flatpak is also a sensible option where available, especially if you want a newer upstream build without depending too much on the base system libraries. Snap is less attractive for many people on Ubuntu Kylin unless they already use it elsewhere, and tarball-only clients tend to be a bit more maintenance-heavy unless you are comfortable managing dependencies manually.

For this distro, I would narrow the field to the following five, with the strongest recommendations coming first:

• Thunderbird
• Proton Mail Desktop
• Tuta Mail Desktop
• Geary
• Evolution

Those five cover the broadest set of needs on Ubuntu Kylin: a full-featured traditional client, two privacy-focused hosted-mail desktop apps, and two lightweight-to-medium local clients that integrate well with a GTK desktop.

What matters specifically on Ubuntu Kylin

Ubuntu Kylin’s technical profile points towards a few practical considerations:

• Package management: native deb packages are the most straightforward choice because Ubuntu Kylin inherits APT and the broader Ubuntu repository model.
• Desktop environment: UKUI is designed to be approachable and familiar, so software with a clean graphical interface and sensible tray/notification handling tends to feel best.
• Translation and UX: good localisation and clear settings are valuable, especially on a distro that is often used by bilingual or Mandarin-first users.
• System integration: mail clients that integrate smoothly with standard desktop components such as file pickers, notifications, certificates, and default app registration are preferable.
• Maintenance burden: avoiding obscure dependency chains is wise, particularly if the machine is used by non-technical family members or office staff.

That is why the strongest recommendation on Ubuntu Kylin is usually a native deb-based client, or a well-supported Flatpak if you want isolation and updated packages.

Comparison table

Why these are the best fit

Thunderbird

Thunderbird is the safest recommendation for Ubuntu Kylin users who want one client that can do almost everything. It handles multiple accounts, IMAP, RSS, calendars via add-ons or integrated features, encryption support, filters, and a large extension ecosystem. On a Debian-based distribution, the deb package is the most natural install method, and the Flatpak is useful if you want a more self-contained desktop app.

Why it suits Ubuntu Kylin in particular:

• Works well with traditional desktop workflows.
• Has reliable IMAP support for most mail providers.
• More forgiving for mixed-language inboxes and large account setups.
• Good option for both home and office users.

Proton Mail Desktop

For anyone already using Proton Mail, the Proton desktop client is an obvious contender. Since it ships as a deb package, it fits Ubuntu Kylin very neatly. That is important, because a native package tends to feel more at home than relying on browser tabs or third-party bridges for everyday use.

Why it suits Ubuntu Kylin:

• Native deb package matches the distro’s package system.
• Good choice for privacy-conscious users.
• Simple interface that works well on UKUI.
• Especially useful if your organisation already standardises on Proton services.

Tuta Mail Desktop

Tuta is another privacy-first option, and on Ubuntu Kylin the Flatpak edition is the one I would look at first. AppImage is available too, but Flatpak usually gives a more consistent desktop experience, better menu integration, and simpler updates. If your focus is secure, encrypted email with a minimal interface, Tuta is a credible option.

Why it suits Ubuntu Kylin:

• Flatpak makes installation and updates straightforward.
• Lightweight interface is easy on a desktop-oriented distro.
• Good for privacy-first personal accounts.

Geary

Geary is a clean, elegant mail client that keeps things simple. It is not trying to replace a full groupware suite rather, it focuses on email done properly. On Ubuntu Kylin, it makes sense for users who want a straightforward, modern GUI without the complexity of a larger office suite.

Why it suits Ubuntu Kylin:

• Simple interface that is easy for non-technical users.
• Flatpak and deb options give flexibility.
• Good for IMAP accounts where you want quick access and minimal fuss.

Evolution

Evolution is the better pick when email is part of a wider productivity setup. If you need mail, calendar, contacts, and task management in one place, Evolution is hard to ignore. It fits Ubuntu Kylin well because it is available as a deb and also integrates neatly with the GTK ecosystem.

Why it suits Ubuntu Kylin:

• Useful for office users and people managing multiple calendars.
• Good desktop integration on Ubuntu-derived systems.
• More feature-rich than Geary without being too exotic.

Clients I would not prioritise here

There are other capable clients on your list, but for Ubuntu Kylin they are generally less compelling:

• Betterbird is interesting, but the lack of a native deb package means it is less convenient here than Thunderbird.
• Mailspring is polished, but on Ubuntu Kylin the snap/deb-only model is less attractive than the stronger options above, and its best features may not outweigh the ecosystem fit.
• KMail / Kontact can work, but it makes more sense on a KDE desktop than on UKUI.
• Claws Mail, Balsa, and Sylpheed are all valid lightweight classic clients, but they are less compelling for the average Ubuntu Kylin desktop user than Thunderbird, Geary, or Evolution.
• aerc, NeoMutt, and Alpine are terminal-based, which makes them better suited to administrators and power users than the typical Ubuntu Kylin audience.

How to install and configure the best three

1) Thunderbird

On Ubuntu Kylin, I would usually recommend Thunderbird first, especially if you need a dependable all-rounder. The deb package is the most sensible route if your repository offers it cleanly, while Flatpak is a good fallback if you prefer containerised apps.

Installation via APT, if available from your enabled repositories:

sudo apt update
sudo apt install thunderbird

If you prefer Flatpak:

flatpak install flathub org.mozilla.Thunderbird

Basic configuration steps:

• Open Thunderbird and add your mailbox with the full email address and password.
• Choose IMAP unless you have a specific reason to use POP3.
• Set sent mail, drafts, and archives to store on the server if you use multiple devices.
• Enable two-factor authentication if your provider supports it.
• If you use Proton, Tuta, or another privacy-focused provider, check whether you need an app password or a specific IMAP bridge method.

For most Ubuntu Kylin users, the key advantage of Thunderbird is that it gives you a familiar, full-featured desktop mail workflow without fighting the operating system.

2) Proton Mail Desktop

Proton Mail Desktop is an excellent choice if your mail account already lives in Proton’s ecosystem. The deb package means it fits neatly into Ubuntu Kylin’s preferred software model.

Typical installation pattern:

sudo apt install ./proton-mail-.deb

If you need to install from a downloaded file and your system complains about dependencies, this is often more robust:

sudo apt install gdebi
sudo gdebi proton-mail-.deb

Configuration steps:

• Launch the app and sign in with your Proton credentials.
• Complete any second-factor prompt, if enabled.
• Choose the folder sync behaviour you want, especially if the machine has limited storage.
• Review notification settings so new mail appears appropriately on the UKUI desktop.

This is the most natural option if you want a privacy-focused service with a desktop client that behaves properly on Ubuntu Kylin.

3) Tuta Mail Desktop

Tuta is the one I would suggest for users who value privacy and want a simple, focused client. On Ubuntu Kylin, the Flatpak build is the better bet because it tends to install cleanly and stay fairly self-contained.

Install via Flatpak:

flatpak install flathub com.tuta.Tuta
flatpak run com.tuta.Tuta

If Flatpak support is not yet enabled on the system, install it first via APT if needed:

sudo apt update
sudo apt install flatpak
sudo apt install gnome-software-plugin-flatpak

Then configure Tuta as follows:

• Sign in with your Tuta account details.
• Allow desktop notifications if you want timely message alerts.
• Check local storage and sync preferences, especially on SSD-limited machines.
• If you use a system-wide dark theme in UKUI, verify the app appearance after the first launch.

Tuta is especially attractive when you want a secure account without the clutter of a giant productivity suite.

Practical recommendation by user profile

• For most Ubuntu Kylin users: Thunderbird.
• For Proton users: Proton Mail Desktop.
• For privacy-first minimalists: Tuta Mail Desktop.
• For a lightweight, clean IMAP client: Geary.
• For office users needing mail plus calendar and contacts: Evolution.

Compatible email services worth considering

If you are choosing a mailbox to pair with Ubuntu Kylin, these services are the ones I would seriously recommend:

• Proton Mail — excellent if privacy is a priority, and it pairs very well with the Proton desktop client. It is a sensible choice for users who want encrypted mail with a polished experience.
• Tuta Mail — another strong privacy-first option, especially good if you want a simple, secure service that matches the Tuta desktop app neatly.
• Fastmail — very reliable, with excellent IMAP compatibility, which makes it ideal for Thunderbird or Evolution on Ubuntu Kylin.
• Mailfence — a solid privacy-oriented provider with standards-friendly support, useful if you want something that works cleanly with traditional desktop mail clients.

In short, Ubuntu Kylin does best with mail software that respects the distro’s Debian-based roots, keeps the interface straightforward, and plays nicely with a conventional desktop. For most people, Thunderbird is the safest all-round answer. If your mailbox is already on Proton or Tuta, their official desktop clients are worth using. And if you want a more integrated productivity experience, Evolution still has a strong case on this desktop.