Thunderbird has long been a favorite desktop-based open source email client app. Apparently, it’s not the only open source email client app out there. There are several other apps you can use as well, in case you don’t like Thunderbird or simply want to compare it with other apps.
A desktop email client app is an app whereby you can access your email inboxes as well as compose new messages. Open source email client apps mean anyone who install the apps should be able to see the source code of the apps, whatever the purpose. Typically, open source software can be used for free, but not always.
If you are an open source admirer and is looking for an open source email client app, here are top 8 apps you can choose.
1. Thunderbird
As I mentioned at the beginning paragraph above, Thunderbird is by far the most popular open source email client app. It is one of the most notable products from Mozilla, a non-profit company behind a popular open source web browser Firefox. Thunderbird was firstly launched in 2003. Since then, this app has transformed to become one of the most popular email client app. Not only in the open source lovers scope, but also proprietary users since Thunderbird is a cross-platform app. In addition to Linux, Thunder is also available for Windows and macOS. Thunderbird supports common email protocols POP 3 and IMAP. It also support multiple accounts. Thunder is released under the Mozilla Public License 2.0.
2. KMail
As you probably can guess, KMail is an open source email client part of KDE project. It is natively designed for KDE desktop environment, but can also runs seamlessly on all desktop environments of Linux. KMail comes with plenty of features including the ability to display plain text only from an HTML mail and integration with popular spam checkers like SpamAssassin and Bogofilter. Same as Thunderbird, KMail also supports POP 3 and IMAP. KMail is a perfect email client app for Linux users who use KDE-based distro. It is highly integrated with other Kontact components.
3. Evolution
Evolution is also a popular enough open source email client app, especially when it was made an official part of GNOME since Evolution 2.0. Compared to Thunderbird and KMail, Evolution tends to lighter and consume less resource so it would be great choice for a lower-specs machine. Evolution is basically older than Thunderbird and KMail. The app has been around since the year of 2000. In addition to accessing email inboxes you can also use Evolution to manage your contact addresses, creating task list, arranging schedules and so on. The source code of Evolution is also available on GitHub.
4. Zimbra Desktop
If you are looking to build an email platform for your company then you should consider Zimbra. Zimbra offers two major products you can implement on your business, email server and email client. In order to ease you in accessing your emails Zimbra also provides a desktop client app. You can also use this desktop email client app to access email from other providers since it supports IMAP and POP3. Zimbra Desktop is a cross-platform open source email client app. Some components of this this app are released under different open source licences. Zimbra Desktop also comes with a number of useful feautures like integrated email search enghine to quickly filter select messages matching with their query parameters.
5. Geary
Another lightweight open source email client app. Geary is also a part of GNOME project just like Evolution. Before taken over by GNOME, Geary was developed by Yorba Foundation. Yorba is the original author of Geary. Geary was intended to bring back users from online webmails to desktop application which, according to Yorba founder, faster and easier. Geary was written in Vala and released under the GNU LGPL v2.1. Geary supports Gmail, Yahoo, Outlook, and popular IMAP servers. This email client also features desktop notification for new messages. The developer team of Geary also provide the source code of this app on GitHub.
6. Claws Mail
With the total file size no bigger than 16 MB Claws Mail is one of the lightest open source email client apps. This app doesn’t also come with too much features like, for instance Evolution. The developers of Claws Mail seem want to emphasize functionality of email client app by not offering complex features and capabilities. You will find no additional features like to-do list, note-taking or calendar. But, standard feature of email client app like address book still available. Claws Mail also supports two major email protocols, POP 3 and IMAP. In addition to Linux, Claws Mail is also available for Windows.
7. Sylpheed
Sylpheed is another super light open source email client. It is lighter than Claws Mail. This app is widely-used as a default email client of lightweight Linux distributions like Lubuntu, Damn Small Linux and Puppy Linux. Since it is super light, the features and capabilities are also limited enough. However, this app also features an address book to makes it easy for to manage frequently-contacted email addresses. If you prefer to use a very simple app then Sylpheed can be a great choice. Sylpheed itself is a cross-platform app. In addition to Linux Sylpheed is also available for Windows and macOS. Sylpheed is released under the GNU General Public License.
8. Nylas Mail
Nylas Mail is a new player in the email client market. This app has just entered the market in January 2017. With its clean and modern interface Nylas Mail seems will be a new favorite email client app for open source fans. Nylas Mail itself is a cross-platform app. The source code of Nylas Mail is available on GitHub under the MIT License. One of the notable features of Nylas Mail is Undo Send which is very useful if you often accidentally send message to the wrong people.