when you click on a link the computer uses your computer settings to determine what to do. what you are wanting the computer to do is open your default browser on the appropriate webpage. This is rarely caused by an issue in Thunderbird. re :if browser opens but gives a blank webpage: This means your computer is opening the default browser eg: chrome. Try these options: Check: Is there an update for Chrome browser, if yes, then update chrome. https://support.google.com/chrome/answer/95414?co=GENIE.Platform%3DDesktop&hl=en Exit chrome. Choose another default browser and then reselect Chrome. Maybe it was something caused in the set up of browser. The following link discusses that setting a stub to operate in background caused an issue. This link helped to resive an issue with chrome not opening. https://support.mozilla.org/en-US/questions/1068267 Just in case your computer is not acknowledging an updated Chrome as the same as previous Chrome..... Exit Chrome Exit Thunderbird Suggest unchecking - or choosing another browser temporarilly eg: IE or Firefox Then resetting everything as default again. Note, it needs to be set in more than one place. Images show settings for Firefox but you would choose Chrome in same location.