Links Not Opening Up in the Browser
If links are not opening up in the browser, here are few things to try:
1) Change your default browser to another browser and then change it back.
In some scenarios after a browser update, the OS setting for the default browser fails to get updated.
2) Use the Postbox Config Editor and make sure the hidden network.protocol-handler.external-default preference is set to true.
3) Use the Postbox Config Editor and make sure the hidden network.protocol-handler.warn-external.http preference is set to false.
Certain add ons (like ThunderBrowse) can leave these hidden prefs in the wrong state after uninstall.