So I upgraded to Thunderbird 3 some time ago. It has nice new features, like the grouped folders. Anyway, there are a few things that annoyed me too; one of them being the fact that whenever someone sends a mail to me and some other people, only the first recipient was displayed, with a “more…” button next to it. The settings unfortunately do not allow to turn this behaviour off, but there’s a hack to do this (maybe in the future, they’ll include a setting…) 

Step 1: find your messenger.jar file

Mac OS X: /Applications/Thunderbird.app/Contents/MacOS/chrome/messenger.jar
Windows: %PROGRAMFILES%\Mozilla Thunderbird\chrome\messenger.jar
Linux: I suggest you run locate messenger.jar to find the file. You might need to run sudo updatedb beforehand for this to work. It might be in /usr/lib somewhere.

Step 2: unzip it

You can either unzip the whole messenger.jar or just content/messenger/mailWidgets.xml from this file, it’s the one we need to edit. On my mac, I copied the messenger.jar to my desktop, renamed it to messenger.zip, double clicked it to extract it, ending up with a “contents” folder on the desktop.

Step 3: edit mailWidgets.xml

Open content/messenger/mailWidgets.xml in your favourite text editor. Find 1 and change 1 to some higher number, like 10. This is line 404 in my file, I found it anyway

Next, we need to change the “true” to “false” in the “singleline=” line here:

  <!-- multi-emailHeaderField: presents multiple emailheaderfields with a toggle -->
  <binding id="mail-multi-emailHeaderField">
    <content>
      <xul:hbox class="headerValueBox" anonid="longEmailAddresses" flex="1"
                singleline="true" <-- change that to false
                align="baseline">

This will make lines wrap around that have too many addresses in it to be properly displayed on one line.

EDIT: This didn’t work for me

Save the file and exit the editor.

Step 4: rezip

I just right clicked the “contents” folder on the desktop and clicked “compress…” so OS X made me a zip out of it again, named “contents.zip”, which I renamed to messenger.jar. I just needed to copy the file back to its original path.

Done!