When I belatedly reviewed Firefox 2 earlier this year (it shipped the previous October), I knew I'd have to do a more timely review of Thunderbird 2, Mozilla's new email client. I've been a Firefox user and proponent for years but I've only sporadically used Thunderbird, largely due to my dedication to Microsoft Outlook, which combines the best email functionality around with excellent personal information management features. Thunderbird, by contrast, is somewhat of a throwback: its roots lie with the late 1990's email component of Netscape Communicator, and it offers email, newsgroup, and RSS functionality, and contacts management, but no calendaring and tasks, as does Outlook. (Mozilla is working on a Thunderbird hybrid, codenamed Lightning, that will add this functionality.) That said, I've been using pre-release versions of this product as my sole email client for almost three months now. And I like Thunderbird 2 quite a bit.

What is Thunderbird?

To many in the Windows world, and to a growing legion of Web mail users, Thunderbird is a non-entity. Microsoft provides a free email client with Windows (called Windows Mail in Vista, but known as Outlook Express in previous versions), and of course, most Office users get a version of Outlook with that product suite. And today, many--especially the coming generation of computer users now still in school--use Web-based solutions like Gmail, Windows Live Hotmail, and Yahoo Mail.

However, there are excellent reasons to use Thunderbird. First, Windows Mail, like Outlook Express, is built on an insecure foundation, and you'd be better off using a free Web-based email solution, like Gmail or Windows Live Hotmail, than these lackluster products. But Web mail solutions aren't offline friendly, and with many of us switching to notebooks, accessing, triaging, and composing email offline is a big deal. Finally, Microsoft has somewhat dulled Outlook's future in the consumer space by removing it from the low-cost Home and Student version of Office 2007. Now, Outlook is available to a much smaller audience and, at $99 for the retail version, it's not exactly cheap. Where are the email users of the future going to turn?

Mozilla Corporation hopes they're going to turn to Thunderbird. It's a complete email solution, with support for POP, IMAP, and Gmail email accounts (and .Mac on OS X), contacts, as well as RSS and USENET newsgroups. It works just fine with multiple accounts of all kinds, features a logical and well-laid out interface, and can be customized in an almost bewildering number of ways. Like Firefox 2, Thunderbird is a somewhat tepid upgrade compared to the previous version (Thunderbird 1.5 in this case). However, since fewer users are familiar with Thunderbird, many new users will be impressed by the wealth of functionality in this product. That it's completely free--and cross-platform friendly, with native versions for Mac OS X, Linux, and other systems--is just the icing on the cake. Indeed, Thunderbird is now the default email client on many of the Linux distributions I test.

When Thunderbird 1.5 shipped in early 2006, Mozilla imbued the application with better security, automatic updating, automatic spell checking, anti-phishing technology, and other useful features. In other words, Thunderbird is already a mature, full-featured product. However, some of the improvements in Thunderbird 2 are absolutely worthwhile and make this an interesting upgrade. Let's take a look.

A look at Thunderbird 2

In use, Thunderbird is a full-featured email solution with all the expected bells and whistles. Here's what's new in this version.

Message tagging

One of the most useful features in Thunderbird 2, message tags allow you to apply tags like "Important," "Work," "Personal," and so on to individual emails. Each tag comes with its own color, so when you tag a message, it is colorized in the mail folder. You can, of course, edit the existing tags and create your own tags. Outlook users will recognize tags as a rendition of the flagging feature in older Outlook versions, or Categories in Outlook 2007. It's as useful in Thunderbird as it is in Outlook, especially since you can auto-categorize email using Thunderbird's Filter Rules (like Outlook's Rules) to parse email when it arrives.

Message history

Users are familiar with the way Web browsers track your navigational progress and the use of Back and Forward buttons is so well-accepted in navigational UI that Microsoft added them to Windows Explorer years ago. Thunderbird adds capability to email, and you'll see prominent Back and Forward buttons in the toolbar that allow you to arbitrarily return to email messages you've previously viewed in the current session. This is the type of feature some users will find quite useful, especially if you tend to triage email by manually clicking on the emails that look most important, regardless of order. Others, of course, will simply ignore this feature, and of course you can remove those buttons (and otherwise configure the Thunderbird toolbar) if you'd like.

Find as you type and saved searches

Thunderbird makes it easier than ever to find the information you need. For individual email messages, a new find as you type feature--identical to that in Firefox--lets you search for text within the current message. Just tap CTRL+F and you'll see the familiar find as you type pane. (ESC causes it to disappear.)

Thunderbird also supports an Outlook-like Saved Searches feature, which is a pretty sweet addition to a free application. Basically, a saved search is a folder that contains the results of a search you previous performed. (In Windows Vista, this is called a Search Folder.) The folder doesn't actually contain the email messages, but is rather a live view of the search results.

To save a search, perform a search using Thunderbird's inline search bar. Then, click the magnifying glass icon next to the search box and choose Save Search as a Folder. A dialog will appear, allowing you fine tune the search or just save it as is. Neat.

Smarter notifications

Thunderbird previously offered Outlook-like "toast" notifications that pop up in the lower-right corner of the screen when new messages came in, but in Thunderbird 2 they've been made even more Outlook-like: Now, in addition to the subject of the email, you'll see information about the sender and the part of the body text when possible. Thunderbird's notifications are usually quite a bit bigger than those offered by Outlook and are more simply styled, but no less useful.

Gmail and .Mac support

Thunderbird 2 natively supports Gmail and, on the Mac, .Mac email accounts, giving users of those systems a way to configure the client in the simplest possible manner. With Gmail, for example, all you need to configure is your name and Gmail account name; after that, Thunderbird will automatically configure itself to access Gmail via POP3 access. Thunderbird is also smart enough to use a non-destructive default configuration (i.e. messages are left on the server by default), and it presents the Accounts management dialog so you can tweak things if you'd like. (A .Mac account is automatically configured for IMAP access.) Kudos to Mozilla for providing this kind of functionality. You can, of course, manually configure Thunderbird or other email clients for Gmail POP3 use, but to do so, you'd have to visit Google's support pages for the configuration information. This makes Thunderbird 2 so much more accessible. I only wish similar support was available for other Web mail types. (This isn't exactly Mozilla's fault, of course: Only paying Yahoo customers can currently use an email client, and Hotmail is notoriously unfriendly to desktop email applications.)

Phishing protection

Thunderbird 2 provides users with what is arguably the most important half of their client-side anti-phishing toolbox: Protection against the emails that try to fool users into visiting malicious Web site that can steal their personal information. Thunderbird will display an IE-like information bar with a graphical red shield any time it believes the currently-selected email is an email scam. You can then tell the application the email is not a scam, or delete it. (This is similar to the way junk mail works in Thunderbird.) Suspicious emails are allowed to display simple text only, so they can't access your system programmatically.

Remote image blocking

By default, Thunderbird blocks remote images in email messages, which is now a standard security feature in virtually all email clients. You can load images by clicking the Load Images button in an email message's information bar or, if you trust the sender, add them to an address book so that images in other emails from that sender will always automatically display. Actually, this is one of Thunderbird's nicest features: When you add a address book contact card in this fashion, you can choose between your personal address book, which is of course typically used for people you know, and a second address book called Collected Addresses. I use this second address book specifically for email newsletters from companies.

Automatic updates

Like Firefox, you can configure Thunderbird 2 to automatically download new product versions and security updates. During the beta, Thunderbird prompted me almost every day to download a new version, which was an interesting way to chart the progress of the client as it improved over time, but now that I've switched to the shipping version, it's been silent. My guess is that we'll see only sporadic updates from now as occasional security fixes and updates are released. You can also manually check for updates via the Help menu.

Add-ons galore

One of the best reasons to use Firefox is its robust collection of extensions and themes, and this is true of Thunderbird as well: Using a Firefox-like Add-ons Manager, you can manage the Thunderbird extensions and themes you've installed, as well as find new add-ons online. This Add-ons Manager also lets you disable and uninstall extensions and themes you don't want, all from a single, convenient interface. (Note that you almost always have to restart Thunderbird to apply new themes or use new extensions.)

In case it's not obvious, extensions are basically software utility add-ons of varying complexity, while themes are user interface styles that can somewhat dramatically change the look of the application. Mozilla installs a single extension in Thunderbird by default--for error reporting--and a single, default user interface theme. I find the default Thunderbird theme to be pleasing and in keeping with the standard Firefox look and feel.

Thunderbird quirks for the Outlook user

The problem with moving from application to application is that the habits and skills you learn in one application don't always translate well to the new one. This is absolutely the case with moving from Outlook to Thunderbird and now, three months later, it's something I still run into on a regular basis. Keyboard shortcuts are an obvious example. As a fast typist, I don't like to lift my hands off the keyboard to grab the mouse. But many of Thunderbird's keyboard shortcuts are just completely different from those in Outlook. Some are the same: The first time I tapped CTRL+ENTER to send an email, Thunderbird asked if I wanted to use that shortcut for sending mail (which, of course, I did). So that worked fine. But CTRL+F brings up the Firefox-based inline find toolbar instead of forwarding the current message; in Thunderbird, CTRL+L is used for forwarding. Ugh.

Now, anyone can learn new skills, of course. The problem is, I've been using Outlook for years, and there are certain actions I perform there that are more muscle memory than anything else at this point. I haven't figured out how to get Thunderbird to not mark messages as read when they're selected, though I did find a place where you can lengthen the amount of time before that happens. This particular feature has been around since Communicator 4.0, I believe, and I hated it as much then as I hate it now. I'm sure you can turn it off: Thunderbird, like Firefox, is hugely configurable through its arcane, Registry-like Config Editor, but you really have to know what you're doing to mess around in there. And of course, the overloaded, multi-tabbed Options dialog can be intimidating as well. (To be fair, Outlook's Option dialog isn't exactly simplistic either.)

Anyway, after a few months of working with Thunderbird, I've come to a somewhat comfortable understanding of how it works, and I can usually grok the differences between it and Outlook without much effort. For those who are not Outlook fanatics, Thunderbird will be an easy transition. Looking forward, however, Mozilla Corporation might consider how they can make it easier for users of Microsoft email programs--and Web-based email providers--to switch to their product. Clearly, there's a lot of good work that could be done there, though Thunderbird is already taking steps in that direction. (Witness the super-simple setup of Gmail and .Mac accounts.)

Thunderbird, of course, doesn't work with Exchange email, unless your administrator configured the server for POP3 or IMAP access. For most individuals, of course, this is a non-issue.

I should also mention, on the flipside, that Thunderbird makes it easy to do some things that are difficult in Outlook. For example, it's very simple to set up Thunderbird so that all of your email is sent through the same account, even replies to emails sent to different accounts. This is possible, but difficult, to configure in Outlook. And Thunderbird supports USENET Newsgroups, which Outlook does not. (However, newsgroup functionality is increasingly less interesting over time, of course.)

Final thoughts

Though it's likely that I'll move back to Outlook full-time at some point (I still use it for calendaring, actually), I have to admit that I had intended to use Thunderbird for about a month and then move on, but it's proven usable and efficient. Thunderbird is an excellent and high-quality email solution, and while I'm guessing that many of the people who read this site haven't really given it a shot, my advice is to do so, especially if you can't get your hands on Outlook 2007. Thunderbird is quite a bit better than Windows Mail or Outlook Express, and while many Web-based email services have improved with Ajax/Web 2.0-based interfaces, users who have to manage a lot of email will be better off with a true email application. And Thunderbird is among the best of those. Is the age of desktop email clients over? I think not, and Thunderbird is among the best evidence I've seen to support that argument. Highly recommended.