Aditya Nag
January 4, 2005

This article was first published on

There has been a lot of news lately about Firefox, the open-source browser from the Mozilla foundation. The Mozilla foundation also makes a e-mail client called Thunderbird which reached version 1.0 recently.

I used Thunderbird for a few weeks to get an idea of what it’s all about, and whether it matches it’s better known sibling, Firefox in terms of features and stability.

Thunderbird is a free download from It is available for Linux, Windows and OS X, and the interface is remarkably consistent across all three. I tested the Linux and Windows versions. It’s a relatively small download, 5.8 MB for Windows, and 9.8 MB for Linux. The installer is simple and easy to use, both on Linux and Windows. In Windows its a standard installer, in Linux it’s a tar.gz file which you need to extract, and then click on the thunderbird executable.

The Interface.

Thunderbird has an intuitive and easy to use interface. All major functions are found as labelled icons across the top in the button bar. Below this are a couple of dialogue boxes which help in sorting and organizing email. The “View” box and the “Search” dialogue box let you easily group your mail or search it. The View box has some pre-defined views, and also lets you make your own custom views. By default, it shows you all your mail, and the other options are “unread”, “last 5 days”, “people I know” and so on.

The other main function is the “search” dialog box. By default, Thunderbird only searches subjects and senders, but you can choose more exhaustive searching if needed.

The rest of the interface is similar to other mail clients like Outlook or Eudora. The left column displays the e-mail account being accessed, while the right-hand window shows a list of e-mail messages displaying things like Subject, Sender, Date/Time, etc.

You can also choose between two more views, the “Wide” and “Vertical” views.

Using Thunderbird.

Thunderbird supports POP and IMAP accounts. I set up three POP accounts. One of these was a Google mail account. The new account wizard is easy to use, and anyone who has set up an account in Outlook or any other mail client should have no problems. For the Google mail account I used the instructions on Google’s website to set it up.

A very important feature for an email client is the import feature. Most people have years of emails and hundreds of contacts stored in their email applications. Thunderbird on Windows ships with a import wizard that lets you easily import email from Communicator 4.x, Eudora, Outlook and Outlook Express. Unfortunately, you can’t import message rules and filters from Outlook, but that is to be expected. In my case, Thunderbird managed to get four years of email and over 600 contacts out of both Outlook XP and Eudora without any problems.

In Linux, you can directly copy your mbox file into the Thunderbird folder. You can also use the wizard to import from Communicator or Evolution.

Multiple accounts and the Global Inbox

Thunderbird can handle multiple e-mail accounts very easily. You can choose to keep different account separated, or put them all together in one Global Inbox. Or you can have some accounts merged together in the Global Inbox, and other independent accounts. Thunderbird also creates separate profiles for each user on the operating system. If your home computer has multiple logins, it will create a new profile for each login.


Thunderbird has a few interesting features which differentiate it from other clients. These are:

Built-in Bayesian spam filtering
Support for popular news protocols: NNTP and RSS

The Spam filtering is surprisingly effective after a week or two of training. Initially it caught around 60-70% of spam, then it went up to about 90%. The number of false-positives was also negligible. This is a good feature, but it may be possible to tweak it to get a slightly better detection rate. Maybe the next version will have this. Thunderbird has options in the control panel to allow you to redirect spam to whichever folder you want. It also gives you the option of not marking items it thinks is junk if the sender is in your personal address book.

Thunderbird also allows you to integrate RSS feeds into it. This is a godsend for news junkies and people who subscribe to a lot of RSS feeds. There are third party tools available which do a better job, but it’s convenient to have it in your mail client. You can also browse through newsgroups. Surprisingly, you cannot use the junk mail filtering on newsgroups. This is a strange omission, considering that Newsgroups get a lot of Spam.

Another great feature is the ability to view emails in the conversation format, just like Gmail. You can do this by clicking an icon which looks like a text bubble. This immediately creates threaded lists of your emails, which makes it easy to keep them in context. This is one of Gmail’s killer features, and it’s good to see it included in Thunderbird.

Thunderbird also has the concept of saving searches as a folder. This makes a virtual folder which has defined criteria to store emails. The emails are stored in the folder, and you can delete them without deleting them from their actual location. You can also choose an option called “Search Online”. This keeps the search folder updated with all new mail from IMAP accounts, as well as News groups postings. This makes sense if you have a broadband connection, but people on dial-up may want to turn this feature off.

Thunderbird comes with a decent spell checker, and allows you to use S/MIME, PGP and GnuPGP encryption. The S/MIME support is built in, for PGP and GnuPGP you will have to use an extension called Enigmail.

The security features in Thunderbird are much better than in Outlook Express or Outlook. Javascript is turned off by default, and attachments are not allowed to run directly. It also blocks remote images by default.

Extensions and themes

The Mozilla Foundation has realized the community’s involvement in the Firefox and Thunderbird projects, and there are some great extensions and themes available. The aforementioned Enigmail, Mouse Gesture support and Dictionary Search are some of the best. More extensions and themes are being made every day, so you are bound to find a few you would like to use.


Thunderbird is a great email client, which can be used as your main email client. One of the best features of Thunderbird is it’s portability. You can take all your mail, address books, and settings seamlessly between Mac OSX, Linux and Windows. It stores email in the standard mbox format, which makes it easy to import into any other client.

I used the Linux and Windows versions, and there was no significant difference between them. If you have used Thunderbird on one OS, you can use it on any OS.

Thunderbird is also available in a variety of languages, twenty two to be exact, including some unusual ones like Turkish, Punjabi and Greek. This makes it perfect for multi-cultural or multi-ethnic work environments.

Thunderbird is not perfect though. It does have a few flaws which need to be ironed out.

One big flaw which I noticed is that Thunderbird defaults to deleting all mail off a POP server. For people who use webmail and POP mail, this can be a disaster. You can lose all your mail off the webserver, if you are not careful. It happened to me, thankfully only on a lesser used account. I think this option should be disabled by default, or there should at least a warning somewhere of this beheaviour in the new account wizard.

The Spam filter could be slightly better or have more options to customize it. Right now, it’s an On/Off feature, with absolutely no customization.

At the end, I must say that Thunderbird is perfectly capable of being used as your only email client. It did not crash on me once in weeks of testing, on either OS. It’s not perfect, but it’s very very good. Go ahead and try it.