Specifications for this cycle :

Default Mail Client

  • Application Role: email client

  • Release target: Karmic

  • Contributors: simon-steinbeiss

  • Field of the spec: 'Application Study'

  • Current application: Thunderbird

  • Studied applications: Thunderbird, Claws-Mail 3.7.1


This is a comparison of the two Mailclients Thunderbird and Claws-Mail (as previously discussed on #xubuntu-devel), to help deciding which should be used in Xubuntu Karmic Koala.

The tests were performed by Simon Steinbeiss between May 7 and 14 2009. The software used was thunderbird (taken from jaunty's official repos) in one corner of the ring and claws-mail 3.7.1-1jauntyubuntu1 (taken from the claws-dev launchpad ppa; slightly newer than jaunty's 3.6.1-1ubuntu1. I decided to take the newer package as it is quite realistic this would be the version to appear in karmic) in the other.

It should be mentioned that I am slightly biased as I have switched from Thunderbird to Claws-Mail and never looked back. I still tried to be as impartial as possible.

Access and Installation

As the "Add/Remove"-Dialog shows only "Canonical Maintained Applications" by default, you will only find Thunderbird in the "Internet"-Section - for Claws you have to switch to "All Open Source Applications". Anyways, if Claws would be the default in karmic, this wouldn't be a drawback as the end-user wouldn't have to install it by hand. Thunderbird's description states "Read/Write Mail/News with Mozilla Thunderbird" whereas Claws says "E-mail client". I have to say I'm not too much of a fan of the slashes in Thunderbird's description as they are more confusing than helpful. Claws' description is maybe too short yet concise. Maybe something like "Read and write Emails" would be more comprehensible.

Thunderbird access

After installation you'll find Thunderbird in "Applications">"Internet" as "Mozilla Thunderbird Mail/News". Quite a long name for an application if you ask me.

Claws access

Claws is in the same section "Internet" as "Claws-Mail", since its name contains its function (nomen est omen) I think it's not necessary to extend this name.


Whichever program is chosen will be installed by default, so the package description matters more for whichever program is not chosen. As stated before Claws doesn't not appear in "Add/Remove" by default as it is in the "Universe"-Repositories. This is imho quite a drawback.

Both package descriptions seem appropriate and easily comprehensible. Claws' description should maybe also mention that it supports different mail accounts - one thing I like about Thunderbird's description.

Thunderbird's description:

  • Thunderbird is a lightweight mail/news/RSS client, based on the Mozilla suite. It supports different mail accounts (POP, IMAP, Gmail), has an integrated learning Spam filter, and offers easy organization of mails with tagging and virtual folders. Also, more features can be added by installing extensions.

Claws' description:

  • Claws Mail is a powerful and full-featured mail client formerly called Sylpheed-Claws. It is also extensible using loadable plugins, which can provide support for additional features, like other storage formats, feed reader, calendar management, mail filtering, etc.


How easy is it to:

  • set up my existing Hotmail, Gmail, generic POP3, generic IMAP account?
  • structure my inbox with folders and filters?
  • import previous inbox from previous client (e.g. vice-versa, Outlook Express)?
  • set up a spamfilter?
  • set up, edit or import an addressbook?


Account setup

On first launching Thunderbird its wizard appeared and asked me the (rhetorical) question whether I wanted to Import "Preferences, Account Settings, Addressbook and other data" but only gave me the option "Don't import anything". Continuing to the next window the "Account Wizard" appeared offering a wide variety of account setups (including "Gmail").

What follows is entering the account information as people might be used to by other clients (like Outlook Express), so "Name", "Email-Address", "Incoming Server">"POP"/"IMAP", "Use Global Inbox", "Outgoing Server", "Incoming User Name", "Outgoing User Name", "Account Name". As a final step you are asked to verify that data in an overview and have the option to immediately start downloading messages. Including the final dialog this makes 7 steps for the initial setup of a generic POP or IMAP account. When trying to setup a Gmail account it only takes 3 steps(!), because Thunderbird is able to fill out all the server-related information for you. The password for the accounts is being asked of you when you decide to download messages (you can decide to store it in the Password manager though).

Obviously when trying to set up a Hotmail-Account things get a bit more complicated. First you have to find out that the extension WebMail helps you with hotmail. When going to Thunderbird's official Addons-Site and searching for Hotmail I couldn't find anything useful, in the end I had to google "thunderbird hotmail". After downloading the extension you have to go to "Tools">"Addons">"Install" and remember where you stored your download (Firefox sometimes tries to install Addons for Thunderbird when you don't click "Save Link As..." as they use the same format.) and install it. After restarting Thunderbird you have to install the extension "Hotmail" available from the same source. Quite a hassle if you ask me (especially when compared to Gmail). Obviously the failure is on Hotmail's side. After another restart you go through a similar procedure as with a Gmail account. (I didn't get this feature up and running as for some reason my local pop-server wouldn't start. A new user also wouldn't get much further than looking into the options GUI in the Addon.) This Addon supports Yahoo, Hotmail, MailDotCom, Gmail, Libero, and AOL.

Folders / Filters

The initial structure of the Folders is the folder hierarchy like this (assuming you chose the "Global Inbox", otherwise there will be a analogous hierarchy above the "Local Folders" with your account name):

  • Local Folders
    • Inbox
    • Unsent
    • Trash

(The "Sent" folder is missing as long as you haven't actually sent a message. The same is true for the "Drafts" folder.)

To create a new (sub)folder, you can either right-click the folder you want your new folder to be a subfolder of (context-menu>"New Folder...") or go to the menu "File">"New">"Folder..." and then choose name and location of the folder in a dialog.

To set up filters, you have to go to "Tools">"Message Filters...". In two dialogs with dropdown-lists you can choose the match-criteria and action. The interface is quite sensible and well structured.


Import Mailbox

I tried to export my Claws-mailbox and import it into Thunderbird. As Claws can export mbox files I thought this should be rather easy. When I went to "Tools">"Import">"Mail" in Thunderbird though, the only option that I was given was to import from "Communicator 4.x" (whatever that may be). To my surprise I wasn't able to import any mail from there. (Maybe someone can verify that.) Even though Thunderbird uses the same format that I exported from Claws (mbox), there was no way of choosing that somewhere in the import-dialog. I assume (haven't tried) that simply replacing my inbox file in my Thunderbird-profile-folder with the one from Claws would work - but seriously: who would do that.


For the spam-filter you don't have to do much to set it up: just press the "Junk" button and Thunderbird will inform you that it needs training to decide what is ham and what is spam. Even though I marked the first test message from my foo gmail account as junk, it stayed inside my inbox. I had to go to "Tools">"Delete Mail Marked As Junk In Folder". There was no way to set up a filter rule to move all junk mail to a separate folder. You have to go to "Edit">"Preferences">"Privacy">"Junk" and toggle "When I mark messages as junk:" "Move them to the account's "Junk" folder". However, even after I toggled this option an email that had previously been marked refused to leave my inbox towards the Junk-folder. Even newly received as-junk-classified messages were not moved to the not-existing "Junk folder" that I would have expected to pop up after toggling the preference to move junk there (like the "Drafts" folder popped up after saving a message for the first time).

Address book

A test import of my address book from Claws (which had been exported in ldif-format) worked fine and without complications. I had to go to the main toolbar "Address Book">"Tools">"Import". From there it was only a few steps to succeed. If I had known, I could have also used "Tools">"Import" in the main window as it gives you the same options to import mail, address book or settings. Thunderbird supports only text-files (LDIF, .tab, .csv, .txt). The addressbook GUI seems to be ok and intuitive. A search bar on the top right helps you to quickly get where you want. Setting up a new "card" (as it's called in Thunderbird) is straight-forward, editing and deleting is the same.


Account setup

On first launching Claws its' setup wizard greeted me and promised that I would be able to use Claws in less than 5 minutes. Basically the wizard looks very similar to the one Thunderbird (and other mailclients) uses. One advantage I see with Claws though is that it offers you to set SSL encryption. The Configuration for a generic POP or IMAP account ends after 6 steps (not showing a summary, maybe a disadvantage to Thunderbird here). In opposition to Thunderbird Claws doesn't have any presets for ISPs like Gmail, so setting up a Gmail account is basically the same as setting up a generic account. This may be seen as a disadvantage by some; but it should also be mentioned that Gmail is the sole(!) ISP that Thunderbird includes as a preset, so I think the advantage is marginal.

With Hotmail again it's a difficult story. Claws recommends in its' FAQ to use freepops, which is in Ubuntu Jaunty's Universe repositories as version 0.2.7-3, the newest version of the software 0.2.9 (including some hotmail fixes, I assume due to the frequent changes in hotmail's protocol). Anyways that's not a big deal (if you ask me) because if you went as far as to read the online FAQ of a mailclient and then went on to freepops website (via the link in the FAQ) it's only one more click to a download of the most recent version of the software as debian package compiled for Ubuntu. After installing both freepops and freepops-updater-gnome (the second is a program that looks for most recent updates to protocols), running the updater (found in "Applications">"Internet">"FreePOPs Updater") I can finally go to setup my account. I go to "Configuration">"Create New Account" and according to the FAQ I set the pop3 server to "localhost" and in the Advanced-tab the port to "2000". The result is a bit sobering:

  • [23:47:18] POP3< +OK FreePOPs/0.2.9 pop3 server ready

  • [23:47:18] POP3> USER ********


  • [23:47:18] POP3> PASS ********

  • [23:47:21] POP3< -ERR NETWORK ERROR

  • *** error occurred on authentication
  • *** Authentication failed.

I don't know what exactly went wrong; it seems that the freepops-server is up and working, but maybe Microsoft changed the Hotmail protocol/website once again and freepops hasn't worked around this yet. From previous experience with this I can say that this method should generally work, even though the connection is really slow. Freepops supports a vast number of domains and it should be mentioned that it can also be used in combination with Thunderbird.

Update: After updating to the latest freepops-protocol versions hotmail works. (14th of May)

Folders / Filters

The initial structure of the folders in the folder hierarchy looks like this:

  • Mailbox
    • Inbox
    • Sent
    • Drafts
    • Queue
    • Trash

For creating new (sub)folders you have to right-click an existing folder. In the menu I couldn't find any entry for achieving this basic task.

To set up filters, you have to go to "Configuration">"Filtering". The dialog is a bit cluttered and something people have to get used to but it still makes sense.


As you can clearly see in this screenshot, it's not as well structured as Thunderbird. You have to go to a new dialog to define your condition and action. (On the other hand the filter management is a lot more flexible and allows more different conditions/settings.) One thing that might confuse newbies here is the use of add, delete and replace. A button called "save" would make a lot more sense I guess. What kinda makes up for that is the option to create a filter based on a message. You can do that by either using the context(right-click)-menu on a single message or by going to "Tools">"Create Filter Rule". This option seems to be the easier and maybe more natural way of creating a filter as the four available options ("Automatically","From","To","Subject") are sufficient in many cases. If you want to edit these filters later on of course you're back on the above described system. Anyways, I think that in the end it's still not such a bad system but Thunderbird is definitely more userfriendly in this aspect.

Import Mailbox

Claws' system of importing mailboxes is quite straightforward, you find it in "File">"Import mbox file". This seems to be the only supported format (apart from Claws' own MH) as far as I could see, but with *most* clients this shouldn't be an obstacle.


If you want to use a local spamfilter you have to either install the SpamAssassin plugin or the Bogofilter. For this testing purpose I installed the Bogofilter plugin and loaded it. Basically all that's left to do is train the filter with the "Spam"/"NotSpam" Button in the toolbar.

If you want to edit the settings of Bogofilter you have to go to "Tools">"Preferences">"Plugins">"Bogofilter". This screenshot should also show how cluttered and unfortunate Claws' preferences-dialog is:


Address book

Importing your address book is simple in Claws. You go to "Tools">"Address Book" and there to "Tools">"Import *** File" (where *** stands for ldif, mutt or pine; those are the three formats supported by Claws). From there on you choose the address-book-file you would like to import and get the options on which fields you would like to import (which you don't get in Thunderbird). To create new entries or to later edit them is similar to Thunderbird, but again it's a bit too cluttered.


The main point of my criticism is that you have to click the "Add" button after you entered an email address, otherwise your changes will be lost when you hit "OK". Otherwise it works ok and intuitive. Claws gives you more options here (connect to a LDAP server for example), but lacks one crucial (and simple) feature: you cannot search your address book. If you want to do that, the easiest way is to compose a new message and use the auto-completion of the "To:" field. That's quite annoying to say the least and asks for a bugreport.

Update: I now filed a bugreport in Claws' bugzilla tracker.

Basic Functions

Here I'd like to describe the differences in some basic functions of the two clients. Apart from what I already described in the above section I think the layout of the programme is a factor that affects its usability

GUI / Layout

Basically both clients support the same layout types. That is the "classic" or "standard", the "wide" and the "vertical" view. Claws has one more layout which is optimised for small screens.

One powerful function that Claws bears is the thread-view. It shows the replies and forwards to one topic in a collapsable tree-view. This can be either de/activated via "View">"Thread View" or toggled via the keyboard shortcut Ctrl+T. This system is really responsive/fast and practical.

Compose Message

The main difference between Thunderbird and Claws in this category is that Thunderbird includes a WYSIWYG-html editor for composing messages. If you want to do the same with Claws, you have to use an external editor via "Edit">"Edit with external editor". Other than that I couldn't notice any significant differences (maybe except from Thunderbird's Contacts-sidepane).

Plugins / Addons

I will only discuss a small selection of plugins for both programmes as there are simply too many out there.


For installing plugins or addons to Thunderbird you always have to go to its' website. There you can search and download your extensions, save them somewhere on your harddrive and then install them via Thunderbird's menu "Tools">"Addons">"Install". (It's really a lot easier to install extensions in Firefox.)


Thunderbird's notification system is integrated and basic (even though there are some additional plugins for that). You can either choose a popup to be displayed or a sound to be played in "Edit">"Preferences">"General".


For Thunderbird there seems to be an integrated solution again, but it doesn't allow you to create certificates, so a newbie would have to go to google from that point.

If you want pgp support things don't look much better. There is a plugin you can find via google called enigmail, but you have to do the setup of pgp yourself.


For installing plugins for claws you can either get one of those available in the repositories or go to their website, where you'll find a few more. When installed you have to load the plugin, which is not the most obvious thing to do. You have to go to "Configuration">"Plugins">"Load". To edit settings you have to go to "Tools">"Preferences">"Plugins".


You first have to install the notification plugin, there is one that simply adds a systray (called claws-mail-trayicon) and one with more features(called claws-mail-multi-notifier). I will discuss the second one. It allows you to display a banner, a popup, execute a command, display a message on a lcd and a systray-icon. Especially the command-option makes it very flexible.


For Claws there is good pgp-support via plugins (pgp-inline and pgp-MIME). On load the plugins ask you to create a pair of keys if you don't have one yet, but you can also do that later via preferences. I would say that usability is excellent and intuitive in these plugins.


Both programs use gtk, but neither of them uses the stock icons from the system's icon set. This results in some visual inconsistency. For both clients several icon-themes are available (Thunderbird-themes at the official Addons-Site, Claws-themes are available at the official site and in the Ubuntu Universe repositories as claws-mail-themes)


Memory Footprint

Testing both clients without plugins loaded results in

  • 15,2MB for Thunderbird (12,5MB heap)
  • 11,4MB for Claws (9,9MB heap)

(Both measured with gnome-system-monitor)


Counting only the required packages (not reflecting the ones that might be installed in Xubuntu by default) this results in

  • 24 packages for Thunderbird
  • 15 packages for Claws

(Both according to

Conclusions / Remarks

Very generally speaking one could conclude that Thunderbird is the more userfriendly and Claws is the more feature-rich client. Thunderbird's memory footprint is bigger (by about 30%) but it also has more features inbuilt (spamfilter, notification). Especially in the filter-setup, Thunderbird seems to have an advantage in terms of user-friendliness. When using Thunderbird I have to say it didn't behave as responsively as Claws. Also I can't really understand why importing emails just wouldn't work with Thunderbird (maybe anyone can confirm this?).

If we look at important features like encryption Claws definitely has an advantage there. Also in terms of dependencies and memory footprint it seems to be nicer. Claws' problems are mainly cluttered dialogs I would say, so a brush up of the GUI would be a great step ahead. Claws is just in general the more flexible client.

Both clients have some problems (like not using stock icons and therefor creating inconsistency), also in terms of usability.

Xubuntu/Roadmap/Specifications/Karmic/DefaultMailClient (last edited 2012-03-25 16:46:54 by knome)