SELKS is a rather specific beast, and that matters a great deal when choosing an email client. Because SELKS is built around security monitoring and threat-hunting, the typical user is not the casual desktop crowd but a practitioner: a SOC analyst, incident responder, researcher, or engineer who may spend most of the day in a browser, a terminal, and a few highly specialised tools. In practical terms, that means the ideal mail client for SELKS should be lightweight enough not to get in the way, but reliable enough to handle secure email, attachments, and account synchronisation without fuss.

SELKS is Debian-based, so DEB packages are the most natural fit. It is also commonly used with conservative, security-focused desktop environments such as Xfce or other relatively lean environments, and in many setups the GUI is either minimal or secondary to the analyst’s workflow. That changes the shortlist quite a bit: flashy, heavy clients are less appealing than tools that are stable, well-maintained, and straightforward to deploy. In SELKS, I would generally favour clients that are available as native Debian packages or as well-contained Flatpaks, with no unnecessary reliance on a sprawling desktop integration stack.

Taking that into account, the most sensible choices from your list are:

• Thunderbird
• Evolution
• Tuta Mail
• Proton Mail
• aerc

Of those, I would actually narrow the “best fit” down further for SELKS to Thunderbird, aerc, and Proton Mail, with Tuta Mail as a good alternative depending on how much you value its privacy model and how you want to structure your workflow. Evolution is perfectly valid, but on SELKS I tend to prefer Thunderbird for general desktop use because it is more widely documented, while aerc is excellent for terminal-heavy operators who live in SSH sessions and tmux panes.

Below is a practical comparison, focused on what matters on SELKS rather than on generic desktop Linux.

Now let’s look at the clients that are genuinely worth considering for SELKS, and why.

Thunderbird: the safest all-rounder for SELKS

Thunderbird remains the most sensible choice for most SELKS installations. It is available as a Debian package, so it drops into SELKS cleanly without requiring any unusual packaging workaround. For a Debian-based distribution used by security professionals, that is a major advantage: you want something that can be installed quickly, updated predictably, and supported by a large community.

Thunderbird suits SELKS well for several reasons:

• It works well in lightweight desktop environments such as Xfce, which are common on security-focused systems.
• It supports IMAP, SMTP, calendar integration, and modern authentication methods.
• It is a practical choice for mixed email environments, including corporate mail, security notifications, and service alerts.
• It is well documented, which matters when you are troubleshooting under time pressure.

In security operations, that “boring reliability” is actually a feature. You do not want your email client to become another incident.

aerc: ideal for terminal-first SELKS users

aerc is a TUI client, and that makes it unusually well aligned with how SELKS is often used. When you are already living in a terminal, a terminal mail client is often the least disruptive option. aerc is especially attractive for:

• analysts working over SSH
• users who prefer tmux or screen
• people automating mail workflows with scripts
• minimal SELKS deployments where GUI overhead should be reduced

Because SELKS is frequently used in operational or semi-appliance contexts, aerc can be a very elegant fit. It does not try to be a full desktop suite, and that is exactly why it works. If your workflow is built around logs, alerts, tickets, and shell commands, aerc feels native to the environment.

The trade-off is obvious: it is not the right choice for users who want a point-and-click interface or who rely heavily on attachments, calendar views, or graphical address books. But for power users, it is excellent.

Proton Mail: the best privacy-first GUI option

Proton Mail is a sensible option for SELKS users who want a privacy-oriented desktop mail app and are happy to operate within Proton’s ecosystem. The official Debian package makes it compatible with SELKS without any awkward conversion, and that is important on a distribution where you would rather avoid unnecessary third-party packaging tricks.

Why it works:

• Official DEB support fits SELKS neatly.
• It is suitable for users who want encrypted, privacy-conscious email.
• It avoids the need to mix desktop-level mail identity with a broader system account structure.

Why it is not always the first pick:

• It is less “general purpose” than Thunderbird.
• It is tightly bound to Proton’s service model.
• It is not ideal if you need a client to handle multiple independent enterprise accounts.

Still, if your organisation already uses Proton, it is a straightforward and respectable fit for SELKS.

Tuta Mail: strong privacy, simple deployment

Tuta Mail is also a good SELKS option, especially if your priority is end-to-end privacy and you want a clean, opinionated client. On SELKS, the Flatpak route is usually the more attractive one because it is easy to manage and avoids cluttering the base system. Tuta is particularly useful when:

• mail is handled under a privacy policy or compliance requirement
• you want a simple GUI client that is easy to explain to non-technical staff
• you prefer a controlled app sandbox rather than installing lots of desktop dependencies

The main caveat is similar to Proton: it is most valuable when you actually want Tuta as a service, not merely as an application. For general operational mail on SELKS, Thunderbird still offers more flexibility, but Tuta is a strong privacy choice.

Evolution: a very respectable desktop client, but slightly less universal here

Evolution deserves mention because it is solid and mature, and it is available in formats that work with SELKS. In environments that lean closer to GNOME, Evolution can integrate beautifully with the desktop. That said, SELKS users are often not asking for rich desktop integration they usually want efficient communication and minimal overhead.

Evolution is best for users who want an Outlook-like feel without actually using Outlook. If your SELKS workstation also doubles as a standard office desktop, it is a good candidate. If it is a focused analyst box, Thunderbird tends to be the more practical recommendation.

Why I would not prioritise the others on SELKS

Some of the remaining clients are perfectly good software, but they are not as naturally aligned with SELKS.

• Geary is clean and simple, but it is a bit too lightweight for a serious operational mailbox.
• KMail / Kontact is powerful, but KDE integration and its broader stack make it more attractive on a Plasma desktop than on a security workstation.
• Mailspring is polished, but I would not prioritise it on SELKS when Thunderbird and the privacy-focused clients are better aligned with the distro’s usual usage.
• Claws Mail is efficient and capable, though a little old-school and less comfortable for users who want a modern workflow.
• Betterbird is an interesting Thunderbird-derived option, but on SELKS I would usually just start with Thunderbird proper unless you have a very specific reason.

How to install and configure the best 3 options on SELKS

1) Thunderbird

On SELKS, the cleanest route is usually the Debian package. If the package is available in your configured repositories, installation is straightforward:

sudo apt update
sudo apt install thunderbird

After launching Thunderbird, configure it as follows:

• Add your email account using IMAP rather than POP, unless you have a very specific archival requirement.
• Set SMTP for outgoing mail with the correct authentication and encryption settings.
• Enable OpenPGP or integrate your existing mail encryption policy if your organisation uses it.
• Disable unnecessary telemetry or optional add-ons where possible.

For SELKS, I would also recommend keeping the mail profile on encrypted storage if your deployment model supports it, because this is often an analyst workstation dealing with sensitive alerts, indicators, and incident correspondence.

2) aerc

aerc is a great choice if you are operating in a terminal-centric SELKS environment. Install it with the Debian package if available:

sudo apt update
sudo apt install aerc

Then configure it using its account settings, usually stored in your home directory. A typical workflow is:

• Set up IMAP for incoming mail.
• Set up SMTP for outgoing mail.
• Use app passwords or OAuth-compatible credentials where the provider requires it.
• Define your mailboxes and identity details.

A practical first step is to create the account configuration file. The exact syntax varies by provider, but the idea is simple: point aerc at your IMAP/SMTP endpoints, provide the login identity, and set your preferred editor for composing messages. If you work via SSH, this becomes especially convenient, because the whole mail workflow stays in the terminal.

3) Proton Mail

Proton Mail is straightforward to install on SELKS as a native Debian package:

sudo apt update
sudo apt install proton-mail

After installation:

• Sign in with your Proton account.
• Allow the desktop app to manage your mail sessions.
• Review notification behaviour so it does not become noisy in an analyst environment.
• Keep an eye on policy settings if your organisation has restrictions around cloud-hosted mail.

If you are using Proton within a team environment, make sure your operational procedures match the service model. In other words, it is an excellent privacy-first tool, but it should be adopted deliberately rather than treated as a generic desktop mail client.

Practical recommendation for SELKS

If I were choosing for a typical SELKS workstation, I would rank the options like this:

1. Thunderbird — best overall balance of compatibility, functionality, and support.
2. aerc — best for terminal-driven analysts and headless or SSH-heavy workflows.
3. Proton Mail — best privacy-oriented GUI option when you are committed to Proton.
4. Tuta Mail — also strong, especially if your team prefers Tuta’s privacy model and Flatpak/AppImage-style deployment.
5. Evolution — good, but a slightly less natural fit for SELKS than the top three.

In short, SELKS is not the place for bloated desktop software unless there is a clear operational reason. The distribution is used by people who tend to value efficiency, predictability, and security awareness. That is why Thunderbird and aerc stand out so clearly, with Proton Mail and Tuta Mail making good sense for privacy-focused deployments.

Compatible email services worth considering

For SELKS users who want a service rather than just a client, the following are the most compatible and sensible options:

• Proton Mail — strong privacy model, works well with Proton Mail desktop, and suits security-conscious workflows.
• Tuta Mail — another privacy-first service, especially appealing if you want a clean, encrypted mail environment.
• Fastmail — excellent IMAP/SMTP support and a very practical choice for professionals who want reliability and standards compliance.
• Mailfence — a useful option for users who want privacy features with more conventional mailbox interoperability.

My strongest recommendations for SELKS are Fastmail for straightforward standards-based use, and Proton Mail or Tuta Mail where privacy and encryption are central requirements. Fastmail is especially practical if you want your desktop client to behave like a normal, dependable enterprise mailbox, while Proton and Tuta are better when the service itself is part of the security posture.