This is what I found working for me: You will need to access the "config editor" in Thunderbird itself.

Open Thunderbird. In 24.6.0, the menu can be accessed on the right hand side of the top menu bar (next to the search bar and is represented by three horizontal lines).

Click Edit > then click Preferences >, a new window will open. You will need to select the Advanced tab, at the bottom of that tab Open the Config Editor.

Then, search for both network.protocol-handler.warn-external.http and network.protocol-handler.warn-external.https.

These two are most likely to have a current value of false. Change the value to true (do this by simply right clicking on them) and the next time you try to open a link from some e-mail it'll ask you which browser to use. Chromium isn't likely to be shown in the list of choices, so use the navigate button. You can find Chromium at /usr/bin/chromium-browser.

If using google chrome as your browser of choice you may want to make it /usr/bin/google-chrome or /usr/bin/google-chrome-stable If Thunderbird doesn't ask you which browser to use when you click on a link after doing this, you can try deleting mimeTypes.rdf file in your profile folder to reset it. The profile folder is typically found as ~/.thunderbird/xxxxxxxx.default/

Original text by Htbaa

In Thunderbird 11.0.1, it is simple, yet not intuitive:

1. Go to Preferences (Menu Edit → Preferences).

2. Click on the Attachments tab.

3. In the Content Type and Action section set HTTPS, HTTP, and FTP to Use google-chrome (or other desired browser).

That worked for me after trying numerous things in terminal that did not work.

Edit -> Preferences -> Advanced -> General -> Config Editor...

Right click -> New -> String

Enter the preference name:

network.protocol-handler.app.http

Value:

/usr/bin/x-www-browser

Setting Default Browser

In the command line, type

sudo update-alternatives --config x-www-browser && sudo update-alternatives --config gnome-www-browser

Solution for the newest Thunderbird version 68.10 and upwards

There is a file now called handlers.json in your ????????.default profile directory under ~/.thunderbird.

Edit or create this file with a text editor while Thunderbird is closed.

Setting "action": 2 and adding {"name":"xdg-open","path":"/usr/bin/xdg-open"} to the first position of the pertaining HTTP and/or HTTPS "handlers: []" list, will launch the default browser or program as specified by the desktop environment.

The handlers.json file should look then like this for the Vivaldi browser:

{"defaultHandlersVersion":{},"mimeTypes":{"text/plain":{"action":2,"handlers":[{"name":"gvim","path":"/home/bin/gvim"}],"extensions":["asc","txt","text","pot","brf","srt"]},"application/pdf":{"action":4,"ask":true,"extensions":["pdf"]}},"schemes":{"https":{"action":2,"handlers":[{"name":"vivaldi-stable","path":"/usr/bin/vivaldi-stable"}]},"http":{"action":2,"handlers":[{"name":"vivaldi-stable","path":"/usr/bin/vivaldi-stable"}]}}}

Preceding mimetypes are for text and PDF.

Solution for newer Thunderbird versions

Solution for older versions using find

1.Thunderbird → Edit → Preferences → Advanced → Config Editor…:

network.protocol-handler.warn-external.http = true
network.protocol-handler.warn-external.https = true

2.Close Thunderbird.

3.At the command line, type:

$ find ~/.thunderbird/ -name mimeTypes.rdf -delete

4.Reopen Thunderbird and click on an HTTP(S)-link. A Launch Application window will open. Click on Choose….

5.Use Ctrl+L to directly enter a /usr/bin/ path to your favourite browser executable, e.g.: /usr/bin/vivaldi-stable

6.Check ? Remember my choice for http(s) links.

7.Open link

Well, I have never used thunderbird but, this looks right -->

When you click on a web link in Thunderbird, it invokes the default web browser for the operating system. It is possible to change this behavior by changing the default browser. On Linux, another way (tried with TB1.5 under Suse and Debian) is to insert the following line in Thunderbird's prefs.js or user.js file (of course put in the correct path to your firefox):

user_pref("network.protocol-handler.app.http", "/usr/bin/firefox");

You can find where Chromium is by typing -->

which chromium

into the terminal.

Source -->

http://kb.mozillazine.org/Changing_the_web_browser_invoked_by_Thunderbird

I tried this solution and it worked:

1) In Settings Manager switch your favourite browser as default browser.

2) update-alternatives --config x-www-browser

3) Follow steps written here

Because none of the listed solutions worked for me, here a different, very drastic way of getting the application to open links in Thunderbird changed:

(E.g. if links currently are opened with Firefox)

sudo apt-get remove firefox-esr

--> open Thunderbird and click on some link --> you can choose a different browser now. Now we can re-install Firefox

sudo apt-get install firefox-esr

None of these solutions worked for me. I ran thunderbird using strace, and discovered, that regardless of what value I chose for network.protocol-handler.app.http, it was always attempting to launch /usr/bin/google-chrome. I searched the preferences, and was unable to find any place where this was defined. In the end, I just did: ln -s chromium-browser /usr/bin/google-chrome , and that seemed to fix it.

There is one other Thunderbird setting you need to check.

Preferences - Attachments - Incoming

The http and https settings there override the OS default and telling Chromium to make itself the default browser.

See this bug: https://bugzilla.mozilla.org/show_bug.cgi?id=724461

And this for the gory details about how the default browser is determined in Thunderbird: http://kevinlocke.name/bits/2012/07/18/thunderbird-default-browser-linux/

This may help anyone stumbling across this later who has it stuck to Firefox

Go to settings control panel, System -> MIME Type Editor, and set each to 'Web Browser':

application/x-extension-html, application/x-extension-shtml, application/x-extension-xhtml, application/xhtml+xml, text/html

Then in settings control panel, Personal -> Preferred Applications, choose chrome

Run sudo update-alternatives --config x-www-browser and choose Chrome

Then launch /usr/bin/x-www-browser and it should start chrome

Then try in Thunderbird.