Welcome Claws Mail, Goodbye Thunderbird [updated] · 5. März 2007, 12:47

(*update*: 2.8.1 was just released, which among other things fixes the GPG-bug)

Ubuntonista had mentioned Claws-Mail (formerly Sylpheed Claws) a couple of times. His opinion of it was so high, and my unappiness with certain aspects of Thunderbird was there, so I gave Claws a shot a few months ago – and quickly put it away. It turns out now that I had installed an old, out of date (and ugly) gtk1 version which is still living in the repositories (that’s what I get for simply trying aptitude install sylpheed-claws). Fortunately this time I went looking at the screnshots on their site and realized I was missing something.
There are recent edgy-packages for Claws available in their own repository which I used this time around, and man, am I glad I did.

What made me switch was the responsiveness of Claws, and the reliability (from what I can tell with my little experience). And both of those points have actually been my major peeves with Thunderbird (which is sort of funny, because I remember similar motivations when migrating from an out-dated outlook to thunderbird in the first place a few years ago). It’s reminiscent of the Mutt slogan “All mail clients suck. This one just sucks less”. In fact I had considered and played with mutt, but even though I am fan of the cli (using screen, irssi, rtorrent etc.) I quickly found out that the cost of switching to mutt was too high for me (too much to learn for efficient use). Whereas with claws an afternoon was enough to migrate and feel comfortable with it.

What drove me away from Thunderbird

Now don’t get me wrong: Thunderbird is a good email client. It was the first that, due to the Enigmail-extension, made GPG usable for me. It was also cross platform, which made my move from WinXP to Ubuntu a breeze. It certainly sucked less than the version of outlook I was using at the time. The difference was relevant enough, that I was willing to give up on the possibility of synching my pdas/phones (which, alas, are all in love with Outlook). And Thunderbird used an mbox format which was well supported by other mail-software and should make my mail archives more future proof.

But Thunderbird was still slow to startup (though better than Outlook back then). I am not a “big” E-Mail user, but I have my fair share of messages: an archive in the tens of thousands, and a steady flow of new messages (and spam). And this is without the majority of mailing-lists which I moved to a gmail-account a while ago. With the increasing of spam of a few months ago, I felt like thunderbird wanted to “compact” my mailboxes every other day – a side-effect of the old and outdated mbox mail storage format which stores all messages of a folder in a single file (and because deleting indivual messages from a large file is costly and slow, it would stay in there, marked as deleted, until it was compacted). Unfortunately Thunderbird doesn’t support other storage formats.

And the mail I had migrated from Outlook – while it was accessible, it was “fragile”. I tried reorganizing my years of mail 2-3 times, and each time something went horribly wrong (good thing I am the type who backs up before doing sth. like that, so restore was not a problem). Mails got lost, folders became undeletable, other folders disappeared and reappeared at will over a few restarts. The trashcan went AWOL when emptying it, until the next restart. I had several file-system folders (with -1, -2, -3 etc. attached) for a single folder in the mail-client, apparently some self-repair magic that recreated “broken” folders. I am not sure how much that was due to the migration from outlook, or whether Thunderbird has a general problem with somewhat bigger amounts of mail, but either way it certainly shook my confidence and raised some doubts on the reliability. I backed up more, and I didn’t dare much reorganization.

Installing Claws and Migrating Data

The latter two are meta-packages which make available a bunch of plugins (you have to enable/load them in Claws if you want to use them, so installing them anyway first, won’t have an adverse affect).

There are scripts that migrate the mail-archives and filter rules from Thunderbird. Adressbook can be exported from Thunderbird to ldif, and then imported to Claws. There’s also a nice “harvest emails from messages/folders” function. Account-Settings for mail and news have to be re-entered manually.

Claws Mail is lightweight and fast

It’s somewhat a cliche for every piece of software to throw around attributes like “fast”, “flexible” and “light-weight” etc., even when the exact opposite is true, so that I now tend to ignore that kind of marketing babble. (One might think that Opensource is more honest in that respect, because of less financial pressure, but that’s definitely not the case – there’s just as many “lies”). The reason I am mentioning this, is because when Claws says it’s the “lightweight and fast email client” – it’s in fact absolutely true. It’s the one thing that immediately made me decide that I have to give claws a fair shake, and see if Claws and me fit together well.

Claws supports several storage formats for the messages. The native format is MH, but maildir++ or even mbox are available. Both MH and maildir store messages as single files, which – together with a moderately modern filesystem – is superior/faster to the Hack that is mbox. The migration-script imported to MH, for my current inbox I use maildir++. Given that there is an “export to mbox” function for folders (and for selected messages), you won’t be stuck if you decide to move at some point in the future (and maildir, like mbox, is well supported in many other clients). No more compacting folders ever again; finally.


I went crazy with my archives and moved thousands and thousands of messages around, finally did the reorganization (simplification) of my archive I had feared so long and had no problems whatsoever. I’ve only been using it a very short time, so I might not be able to conclusively judge this point, but one things for sure already: it sucks a lot less than Thunderbird in this respect.

Usability & Features

Claws, like Thunderbird, makes it easy to get familiar with the basics. But while Thunderbird always felt like it hides lots of information away to make things less intimidating for new users, Claws provides more information, be it the mime-types of attachements, the number of messages in every folder, mail-headers that are just a keyboard shortcut away.

I also found search to be much more powerful than in Thunderbird. Recursive search in folders with very flexible criteria, and even regular expressions, makes it easy to find messages. And not only are they found, but they are also presented in context, that is, the folders that have matching messages get a little search icon and matching messages can then be viewed on a per folder basis.

Claws provides plenty of keyboard shortcuts which makes for fast usage.

Claws has much more features than Thunderbird, however they won’t get in the way if you don’t care for them (and ironically Claws still manages to be a lot more responsive than Thunderbird). For example several functionalities are implemented as plugins by the core team, so they are not even enabled by default. Rather than enumerating features, I think the respective goals (as perceived by me) puts it more succinctly: While Tunderbird seems to work hard on the problem of how to appeal to new email users, Claws seems to invest a lot of time and effort to think about the problems that people have that use mail a lot or have been using mail for a long time.

The little things are just right

There’s plenty of neat little things, that make you enjoy using Claws. Like the pdf-viewer plugin, which is very fast (notice a common theme here?) compared to opening it in evince. Or the way that hooks, plugins and filters are implemented. Or the tray plugin with a visual indicator of new mail. Or the way that quoting is implemented (partial quotes, cut and paste quotes etc., hiding and unhiding of deep quotes). Dealing with Mailing-Lists (using metadata to offer subscribe/unsubscribe/view “homepage functionality in the menus; automatic renaming of subject lines with regexes). The way offline-working and synching is implemented (though granted, Thunderbird did is very well, too, I was [unnecessarily] afraid Claws would be a regression in that respect).


And while Claws does plents of things different than Thunderbird, there’s not anything material missing. S/Mime i still a bit difficult to set up apparently, but I don’t use that. PGP/inline and PGP/Mime on the other hand are easy to set up and use and they work well (though I am missing the toolbar-buttons for easy access on the message-compose screen from Enigmail). There’s also a bug in the recent release (2.8.0) which crashes Claws when viewing an encrypted PGP/inline message, which no doubt is pretty serious – though it’s fixed in cvs though, and the next release will hopefully be soon (*update*: 2.8.1 which fixes this, was released today). This made me initially push bask my migration, but I couldn’t stand Thunderbird after having used Claws.

Reorganizing my archives I also found a few mails (created with old version of outlook express), that had (mime-)attachments which Claws could not properly save/open, apparently a few bytes went missing (unzip complained). I’ve talked with the developers on irc (another plus-point! Try that with thunderbird…) and at this point it’s not clear whether this is a problem with the attachments, or a bug in the mime-decoding. Saving the complete mail and opening the message in Thunderbird makes the attachment available though. And since no mails from recent years (be it zip or not, outlook express or not) are affected, this is not a deal breaker for me.

And there are also odd little quirks, for example you can’t move folders to mailboxes of a different format sometimes (e.g., a folder from an MH to a maildir++ mailbox), but you can move all messages. The account-configuration is a modal box (meaning it blocks using Claws until it is closed). The way recursive search works is not obvious right away (or it just wasn’t to me), but it’s easy to use once your told (the people on irc/freenode #claws are nice and very responsive as well). [edit to add:] And retrieving mail blocks the UI, so timeouts (for example with IMAP) can be pretty annoying, though at least the timeout-wait is configurable.

So, yeah, Claws Mail is not the perfect mail client either, but nobody honestly would believe that about any client anyway. But…


...it is leaps and bounds better than Thunderbird. It’s very responsive, uses resources conservatively, has lots of useful features, and it is rewarding to use and learn. It’s also very under-recognized, which after using it for a while is rather inexplicable for me. You should seriously give Claws Mail a try. With the recent name-change away from Sylpheed-Claws, you won’t even have to worry about spelling it right anymore.

Did I mention Claws Mail and everything around it was very responsive? I guess I did, but it doesn’t hurt to mention it too often.