8 Greatest Open Source Email Clients for CoreOS in 2026
Reviews, comparison, screenshots and more for the 8 greatest open-source email clients for CoreOS.
Email Client Screenshots
Mozilla Thunderbird
Mozilla Thunderbird is an open-source email client for CoreOS and is written in the JavaScript & C++ programming language. The official description from its website says, "Access all your messages, calendars, and contacts in one fast app."
Balsa
Balsa is an open-source email client for CoreOS and is written in the C programming language. The official description from its website says, "Balsa is an e-mail client for GNOME, highly configurable and incorporating all the features you would expect in a robust mail client."
Claws Mail
Claws Mail is an open-source email client for CoreOS and is written in the C (GTK) programming language. The official description from its website says, "Claws Mail is an email client (and news reader), based on GTK+..."
GNOME Evolution
GNOME Evolution is an open-source email client for CoreOS and is written in the C (GTK) programming language. The official description from its website says, "Evolution is a personal information management application that provides integrated mail, calendaring and address book functionality."
GNUMail
GNUMail is an open-source email client for CoreOS and is written in the Objective-C programming language. The official description from its website says, "An email client for GNUstep."
Geary
Geary is an open-source email client for CoreOS and is written in the Vala (GTK) programming language. The official description from its website says, "Geary is an email application built around conversations for the GNOME desktop."
KMail (Kontact)
KMail (Kontact) is an open-source email client for CoreOS and is written in the C++ programming language. The official description from its website says, "KMail is the email component of Kontact, the integrated personal information manager from KDE."
Sylpheed
Sylpheed is an open-source email client for CoreOS and is written in the C & GTK+ programming language. The official description from its website says, "Sylpheed is a simple, lightweight but featureful, and easy-to-use e-mail client."
Email Client Comparison
| Name | Description | Screenshot | Platforms | Language | Website | Wikipedia |
|---|---|---|---|---|---|---|
| Mozilla Thunderbird ⭐ Recommended | Access all your messages, calendars, and contacts in one fast app. | Screenshot |
| JavaScript & C++ | Website | Wikipedia |
| Balsa | Balsa is an e-mail client for GNOME, highly configurable and incorporating all the features you would expect in a robust mail client. | Screenshot |
| C | Website | Wikipedia |
| Claws Mail | Claws Mail is an email client (and news reader), based on GTK+... | Screenshot |
| C (GTK) | Website | Wikipedia |
| GNOME Evolution | Evolution is a personal information management application that provides integrated mail, calendaring and address book functionality. | Screenshot |
| C (GTK) | Website | Wikipedia |
| GNUMail | An email client for GNUstep. | Screenshot |
| Objective-C | Website | Wikipedia |
| Geary | Geary is an email application built around conversations for the GNOME desktop. | Screenshot |
| Vala (GTK) | Website | Wikipedia |
| KMail (Kontact) | KMail is the email component of Kontact, the integrated personal information manager from KDE. | Screenshot |
| C++ | Website | Wikipedia |
| Sylpheed | Sylpheed is a simple, lightweight but featureful, and easy-to-use e-mail client. | Screenshot |
| C & GTK+ | Website | Wikipedia |