Practical add-ons for Thunderbird


© O.M., Fotolia

© O.M., Fotolia


Mozilla Thunderbird email client continues to gain ground thanks to its multitude of internal features, and add-ons help to extend its functionality.

The Mozilla repository has no fewer than 800 add-ons for Thunderbird alone. Keeping on top of this collection is difficult. In this article, I'll introduce five must-have add-ons.

In many cases, the Thunderbird mail client works quickly and efficiently, but no program can be a master of everything, and in some cases, functionality has been sacrificed to keep the program lean. Add-ons help users by restoring the features the developers left out.


To manage these practical helpers in Thunderbird, go to Tools | Add-ons…. The Extension Manager (Figure 1) lists extensions, language packages, and themes (i.e., files that define the appearance of the GUI). The Download extensions link takes you directly to the Mozilla repository [1], which offers numerous add-ons.

Figure 1: The Extension Manager gives users centralized add-on management.

When you get there, you can download the .xpi file and press Install… to integrate the add-on with the extension manager. Firefox or SeaMonkey users need to right-click the corresponding XPI file and select Save target as…; otherwise, the add-on will end up in the browser.

Additionally, many add-ons are available directly from the package managers of most Linux distributions, although the version might not be the latest release. For example, Ubuntu has an enigmail pack for the Enigmail plugin. Because most extensions have an integrated, automatic update mechanism, you can simply install from the Mozilla repository to get the latest version.

Correct Identity

If you use a single account to manage multiple mail addresses – or Identities in Thunderbird terms – you will be familiar with this problem: When you reply to a message, the sender address in the header is wrong and the mail might not even reach its recipient. A workaround for this involves setting up a separate mail account for each address; however, this tends to cause confusion.

The Correct Identity add-on [2] helps to select the right identity for a reply on the basis of the recipient's address. Installing the helper program is easy – just use the Extension Manager, which is also where you configure the plugin. The clear-cut dialog provided by the add-on shows you two tabs: Selection and Detection. Selection is used to specify the identity you want to use as the default in the context of each account. To do this, select the account below Account and the matching identity below use.

Correct Identity really comes into its own when you enable the attempt to find and use an identity that appears in its recipient list option. Then you can use the second tab to specify the rules to apply for selecting a sender ID (Figure 2). Because a separate ruleset is available for each identity, you must first select Identity to choose one.

Figure 2: The Correct Identity add-on helps you manage multiple sender addresses for each identity and includes a ruleset for email address selection.

The plugin understands regular expressions [3], which you need to enclose in slashes:

/(me|myself|other.*?) @email\.provi\.der/

Also, you can enter a string for simpler filter rules (Figure 2).

In the previous example, Thunderbird automatically selects the sender address of if the recipient is or the message is directed to any recipient in the domain. However, automatic sender selection only works for replies to email, not when you are creating a new message. When creating a new message, you will still need to select the identity manually.

NestedQuote Remover

Losing track of extended email conversations is easy, especially on mailing lists and in mail that includes too many nested quotes (Figure 3). Manually removing superfluous quotes is time-consuming. The small but impressive NestedQuote Remover add-on [4] takes this task off your hands.

Figure 3: Multiple-level quotes can be removed automatically or by pressing a keyboard shortcut in NestedQuote Remover.

After using Extension Manager to install NestedQuote Remover, you can configure the helper directly in the same dialog. The first setting relates to the maximum permitted quote depth (i.e., the number of quoting levels that you want to keep in your replies). In practical applications, the default of one level worked well.

Selecting automatically delete nested quotes tells Thunderbird to remove any quotes below the preset depth when you reply to mail. As an alternative, you can enter a Shortcut for semi-automatic quote removal in replies.

As a default, the developers have assigned Ctrl+Shift+N, which means that you can decide individually for each message whether to keep or remove the quote.


NestedQuote Remover has a close cousin called QuoteCollapse [5] that offers the same functionality when reading email as NestedQuote Remover offers when replying. In contrast to other extensions, this add-on is not configured in the Extension Manager.

The project homepage lists tips for modifying the tool's behavior by editing the configuration files.

When you open a message with multiple quote levels, Thunderbird first uses a compacted view (see Figure 4), thus saving space. If you need more information, you can expand each level successively by clicking on the small "+" character (see Figure 5). The plugin improves readability and visibility, especially for extended discussions on mailing lists. Unfortunately, QuoteCollapse developers only officially support Thunderbird up to version 1.5, but not 2.0 or newer. In our lab, the plugin worked perfectly with more recent versions of Thunderbird.

Figure 4: QuoteCollapse comes up with a compact view of the quote levels …
Figure 5: … but will expand them at the press of a button.

To install the plugin on these versions, use a workaround. First, create a key called extensions.checkCompatibility of type Boolean and with value false below Edit | Settings… | Advanced | General | Edit Configuration…. This keeps Thunderbird from checking the add-ons for compatibility at start-up time. A word of caution: This applies to any extensions you have installed and could cause unanticipated problems.


Quicktext [6] helps users quickly insert signatures or text blocks into messages. Compared with other extensions covered in this article, Quicktext has the biggest repertoire of functions.

In addition to all of the features offered by the free version, the commercial Pro variant includes options for using a script engine or sharing templates from a shared resource with other users. In this article, I'm only covering the powerful and free version.

By default, Quicktext gives Thunderbird the ability to assign a signature to each identity, and the signature changes depending on the sender selection.

If you need a single identity for multiple signatures – for example, for private and business events and different languages – the integrated signature management program just won't cut it, which is precisely where Quicktext is needed. It saves various text blocks as templates, which are available as keyboard shortcuts.


In contrast to Thunderbird, Quicktext does not automatically insert a separating line before the signature, so you will need to add the line manually.

Inserting Keywords

Start by configuring the keyboard shortcuts in the General tab of the program preferences, which you can access via Tools | Quicktext.

Then add a group in Templates. Although you could call the group Signatures, this title is only used internally. Next, use the large text field to add the signature itself. To extend the signature as needed, you can use variables. Finally, define a Shortcut.

In the previous example (Figure 6), pressing Alt+1 while composing an email inserts a signature titled private. Alternatively, you can use the toolbar that Quicktext integrates with the message editor.

Figure 6: Quicktext adds this signature to the message when you press Alt+1.

Besides managing signatures, Quicktext also understands keywords, which give users a convenient approach to inserting standard phrases with the press of a button. The configuration is similar to setting up signatures. First, create a template, preferably in a group of its own. Instead of entering a keyboard shortcut, this time enter a keyword, for example, wkr for With kind regards (Figure 7).

Figure 7: A time-saving feature lets you add common phrases with the press of a button.

In the future, when you compose an email, you can simply type wkr and press Tab to tell Quicktext to insert the text block. This is a useful timesaver, especially for users with a heavy email load, and you can start thinking about adding more set phrases.

Show InOut

If you manage incoming and outgoing mail in the same folder, you will probably lose track of something eventually. Thunderbird does not use tags to tell you whether a message is incoming or outgoing. Besides this, the software only shows either the recipient or the sender of the email, depending on whether you sent or received the message, but it does not do so dynamically (Figure 8).

Figure 8: The mail overview looks cluttered without the Show InOut add-on.

The Show InOut add-on [7] lets you change this behavior. The installation follows the standard Extension Manager-based approach and does not require any special configuration.

After restarting Thunderbird, you will see new columns in the mail overview, which you can select in the normal way by clicking the list pictogram on the right. To be more precise, the plugin adds two options: In/Out and Counterparty. The former displays a symbol to tell you whether this is an incoming or outgoing message, whereas the latter shows the recipient or sender, depending on the message type.

If you insert the two columns and at the same time remove the legacy sender and target columns, you should see something like Figure 9. Thunderbird shows you the sender for incoming mail and the recipient for outgoing mail. The Show InOut website lists additional features that allow users to customize the add-on to suit their own needs.

Figure 9: Show InOut gives you a clearer view of messages you have sent and received.

Thunderbird has a powerful add-on interface that lets users extend its functionality. The "More Add-Ons" list does not claim to be complete, but it might whet your appetite.

More Add-Ons

The Enigmail plugin encrypts email messages with GnuPG [8][9]. Lightning, the calendar add-on, was covered in the April 2008 issue of Linux Magazine [10], but there are many more add-ons.

Attachment Sizes gives you an overview of file attachment sizes in incoming and outgoing messages [11]. Forward extends the button for forwarding messages, adding a function that alternatively embeds or attaches messages for forwarding [12]. MozPod is a really practical helper for synchronizing the Thunderbird address book with your iPod to make sure you have all your contact data with you all the time [13]. Unfortunately, the tool currently works on Windows or Mac OS X, but not on Linux.

The Select Inbox add-on [14] tells the program to open your email account's inbox directly when launching, even if no account is set to check for new email automatically. Thunderbird does not let you tag mail as having been replied to or forwarded, and if this bugs you, ToggleReplied is the tool you need [15]. Finally, you can remove annoying brackets in the subject line of a forwarded mail with QuoteAndComposeManager, which also offers a number of other interesting features [16].

The Author

Florian Effenberger is the international marketing project co-lead and marketing contact for German-speaking countries with, and he's a board member for the non-profit Germany organization. Florian specializes in designing and managing open source-based school networks. You can contact him at