Testing Thunderbird 3: What to do if it ‘shreds’ your threads

I use Mozilla Thunderbird at work for reading my email and, since Mozilla Messaging is approaching the release of Thunderbird 3, I decided to give the latest beta a try. I’m an Ubuntu user (8.04 “Hardy Heron” on my workstation) so I sought out a PPA for development versions of Thunderbird, and came across ubuntu-mozilla-daily. I added the repository to my apt config and you can too, here’s how:

Add the following lines to /etc/apt/sources.list using your favourite editor.

# Thunderbird 3.0 beta builds from ubuntu-mozilla-daily
# sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 247510BE
deb https://ppa.launchpad.net/ubuntu-mozilla-daily/ppa/ubuntu jaunty main
deb-src https://ppa.launchpad.net/ubuntu-mozilla-daily/ppa/ubuntu jaunty main


Note: Pardon any wrapping that may occur. It’s really four lines, two of which start with a comment ('#'), one with deb and one with deb-src. Also, be sure to replace the text jaunty with the version of Ubuntu you are using. The ubuntu-mozilla-daily PPA linked above can produce these lines for you if you are unsure. Just click the link that says ‘Not using Ubuntu 9.10 (karmic)?’

When you have added the repository to apt, you will need to run the apt-key command listed in the comment above in order to add the signing key to the apt keyring. If you don’t, you’ll receive warnings that the package cannot be verified. Also note that adding the repository this way may cause apt to report that there are updates available for other installed packages. I haven’t tested that particular detail as I was doing this within the confines of a virtual machine.

Once this is done you can install Thunderbird 3 using the following commands:

sudo apt-get update
sudo apt-get install thunderbird-3.0


There will now be an entry in Applications -> Internet named Shredder 3 Mail/News. Upon running it and going through setup of my account, one of the first things I discovered is that Thunderbird 3 was not threading by subject as I had been used to. I spent some time researching why this had changed and if the behaviour was configurable. Eventually I came across a page on the Mozilla wiki that explained Thunderbird’s threading implementation in detail.

It turns out that the default value for two of the settings controlling thread behaviour changed between versions. By default, Thunderbird 3 uses strict threading which means that threading by subject is disabled. There are two settings that control this behaviour though: mail.strict_threading and mail.thread_without_re. The first setting enables/disables threading by subject while the second allows subject-threading even if “Re:” isn’t present. According to the wiki page there is also a setting new to the 3.x branch called mail.correct_threading which threads correctly regardless of the order messages are added to a folder.

These settings are important to me, as the ticketing system Pythian uses sends email notifications when requests are updated/modified, and it cannot use the References and In-Reply-To message headers. Also, the subject of these messages does not include the text “Re:”.

All of this means I needed to toggle the three thread-related settings from their default value in order to get the behaviour I expect. To do so I went into Edit -> Preferences -> Advanced and clicked Config Editor. After promising to be careful I filtered for “thread” and observed the following settings and their values:

I double-clicked each of these to change their value and closed the dialog. I refreshed the view of my inbox and . .  .  still no threading! It occurred to me that I would need to rebuild the index, so I went into Edit -> Folder Properties and clicked the Rebuild Index button. I have a rather large inbox, so after going to get a coffee and checking in a while later I found that Thunderbird 3 was now displaying messages in my inbox in exactly the same way as had the previous version.

Now that was out of the way, I could continue with exploring the rest of the features the new version Thunderbird has to offer, including new search functionality with advanced filtering, and user interface improvements such as a tabbed interface and redesigned toolbar.