Linux Mail Clients Deep Dive: Thunderbird

E-mail has been around forever, predating even the web. Despite its age, and the continuous influx of new messaging platforms, it remains the most widely employed form of electronic communication. It offers a combination of reliability, ease of use, flexibility, with an open and non-proprietary structure that appeals to both new and seasoned users. When it comes to accessing e-mail the options are numerous and the choice can be deeply personal.

Most e-mail services offer web-based interfaces that can be accessed through any device and with any operating system. While this can provide users with basic functionality, many users require a dedicated mail client for expanded functionality, the ability to review messages offline, and for managing multiple accounts. In this series of reviews, the ItsMOSS team will review the various mail clients available to Linux users and share our experiences.

Mozilla Thunderbird

Thunderbird is developed by MZLA Technologies Corporation, a wholly owned subsidiary of the Mozilla Foundation. Thunderbird has been in active Open Source development for close to 18 years. It is available for Linux, macOS, Windows and unofficially on FreeBSD and OpenBSD. The built-in features are many.

  • Calendar, local and remote server
  • Chat via IRC and XMPP compatible services
  • RSS Feeds
  • Address Books local, LDAP and Text file import
  • Usenet News Groups
  • Filelink service functionality for WeTransfer, Nextcloud, Dropbox and Box
  • Event and Tasks
  • End-To-End Encryption via OpenPGP and S/MIME

To further add to the functionality, Thunderbird supports Add-on programs. These Add-ons are similar to the extension feature of Web Browsers. I have personally used it on Windows and Linux off and on since it was released.

Installation and setup

Thunderbird can be found in most repositories along with Flatpak, Snap and Appimage. If it’s not already installed in your Linux Distribution. Once installed and opened for the first time, you will be prompted to configure your mail account or accounts. By default it supports POP3 and IMAP, with Microsoft Exchange accounts needing an Add-on to work. Once you type in your name, email address and password, Thunderbird will look to see if it already has the configuration for that provider; if it does, you are done. If not you will be prompted to enter the details specific to your provider. An Exchange account will require the installation of a Add-on and adding your account details to that Add-on. There is also the option of importing mail messages, address book entries, feed subscriptions from compatible applications.

My use case

I’ve been using email for close to 30 years. I started out using Pine, which was a text based email client which used the ncurses interface to give it a somewhat graphical interface. There was no mouse control: you would use the keyboard arrow keys and the enter key to navigate. I would dial in to the University with my modem. I have seen the advancement of email clients over the years. After entering the office workforce in the mid 90’s, I began to use Lotus Notes and Outlook. For my personal email I continued to use Pine for many years until switching to Eudora and then to Thunderbird. After changing careers, I no longer had an employer-provided and -supported email account, and one thing I missed was the ability to see sent emails and read emails despite what computer I was using, due to limitations of POP3. Since the invention of browser based ‘Webmail’, I started to use it to resolve that issue. Once Email providers began offering IMAP, which allowed for two-way folder synchronization, that revived my interest in mail readers.

User Experience

Thunderbird’s functionality is very similar to other email clients mentioned in our previous articles. Your accounts’ folders are on the left panel, with the contents of the selected mail folder in the center panel. Below that is where your selected message is displayed. These windows can all be adjusted by dragging them; optionally, you can display a single day of calendar events in a panel on the right. You can also customize the tool bar by right clicking on it and selecting customize. Other options are available via the View menu, or, if the menu bar isn’t shown, press the alt key on your keyboard.

If you have used other mail clients, you will find similar behavior in Thunderbird. Replies are defaulted to in-line, where the message is quoted below where you would enter your text. Forwarding a message follows the same format as a reply, with the original subject, date, from and to fields listed below. Creating a draft message is very simple, just click on File from the menu bar and select save. That message will then appear in the Draft folder in the left panel; to re-open it, select it from the Drafts folder and resume typing. Once you press the Send button it will be removed from the Drafts folder and placed in the Sent Mail folder. The Address Book is only needed if you are editing or adding new entries. After clicking on Write to create a new message, simply start typing in the name in to the To field, it will automatically display matches in a pop-up window directly below. There is a bit of contention over Address book synchronizing along with the Calendar (more on that below) if you are coming from Outlook. Since that is a native function of the Exchange server. Thunderbird attempts to solve that via text file import using such formats as LDIF, TAB, CSV, TXT and VCard (VCF) or via a Add-on app like TBSync.

The default Calendar integration is not as robust as Outlook. It will prompt to add an event to the calendar if the person sent an ICS file as an attachment to the message. If HTML links are present in the ICS file, they will be preserved in your calendar entry. An ICS file is a standard iCalendar file format that most if not all clients support. Thunderbird does natively support LDAP and iCalendar (not an Apple product). You have the option of importing an ICS calendar file or using a remote ICS service. In order to support CalDAV or CardDAV you will need an Add-on. Synchronizing depends on the provider; some will only support 1-way sync (download from the service to your computer) and others support 2-way sync. Better, and perhaps easier, functionality can be gained by installing an Add-on calendar app replacing the existing default feature.

Over the years Thunderbird has been a popular choice, compared to the paid version of Microsoft Outlook available in MS Office. Thunderbird was still a go-to choice even when Microsoft released Outlook Express, which was a feature-reduced version of Outlook available in Windows. Within the past decade, the look and feel of the various mail clients have kept up with current norms. Many will say the same is not true of Thunderbird; despite the appearance upgrade 4 years ago, it still looks a little outdated. I can’t say I blame them, I think MZLA’s design is more of function over form. It doesn’t mimic the interface that the other current mail clients use. If you used Thunderbird a decade ago, you will see that it hasn’t changed. The Get Messages, Write, Address Book, etc tool bar icons are in the same location and order. The calendar looks and functions the same. That is not to say that they haven’t mimicked other designs. In the past few years they decided to hide the file menu by default (to view the bar you would press the alt key).

When Microsoft released Office 2007 with their new Ribbon Tool Bar (which shouldn’t be confused with the Ribbon Design concept of the late 80’s and into the 90’s) they called it “The Fluent UI”, and it was further refined in future versions. Thunderbird did not make a similar design change, which leaves it looking more dated.

I should say more about the Add-on feature of Thunderbird, one feature which sets it apart from other E-Mail Clients. Unfortunately it is not all roses. The Add-on feature works similarly to the Web Browser Extensions or Gnome Shell Extensions. The Achilles heel of Thunderbird’s Add-on functionality is that a change can essentially break the Add-on. As with the Add-ons of the aforementioned products, they are not all maintained by MZLA, but are independent developers, in many cases donating their time and efforts creating the Add-on. Generally you will not have a problem, but when you do, you are at the mercy of the developer of that Add-on. The Add-on system in Thunderbird will only let you add Add-ons that are compatible with your version. Even if you try to manually install it, Thunderbird will disable it if the Add-on is not compatible with your version of Thunderbird. When this happens, it obviously upsets a number of people. Many will call out the Thunderbird developers to not fix what isn’t broken. This type of issue has been going on for years and not just with Thunderbird: Gnome Shell is notorious for updates that break extensions for example.

Version 78 was released last summer, with an overhauled Add-on system which left many Add-on’s unsupported. It was up to the developers of each product to update their Add-on. I will point out that not all Add-on providers are providing their software for free. There are some who offer products for a fee, and those have a more-vested interest in keeping up with updates. This is not to say that free developers do not attempt to keep up with updates, but they may be less motivated to, or may be too busy with paid projects.

When I updated to version 78 from the version 68, I lost the ability to use gContactSync, which was an Add-on to sync my Contacts from Gmail. I searched for a replacement and found TbSync; this supports CalDAV, CardDAV, Google and Exchange ActiveSync (EAS). If you are using OwnCloud, NextCloud or iCloud then you are covered because they use CalDAV and CardDAV. Replacing gContactSync with TbSync wasn’t a big deal, just a bit of an annoyance.

Final Thoughts

Over the years I have found Thunderbird and the Add-on system to be reliable, though it can be a bit annoying at times. I have never felt that it was lacking any functionality I needed, due to the Add-on features. It may not be very flashy like other E-Mail clients but it will get the job done. I would not have any reservations using Thunderbird as a Outlook replacement when used with a well-supported Add-on for MS Exchange support. For personal use, it is quite usable in its default configuration, though it is not as lightweight as Geary, Claws, or KMail.

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