I have been using Thunderbird for some time without any problem. I have now found I cannot open Thunderbird when trying to contact website email links. Normally when clicking on an Email link Thunderbird opens a window on top of the browser, whatever browser I am using. Now it doesn't, in Safari it shows an error message along the lines " Microsoft windows doesn't recognise email addresses starting 'mailto' I discovered this problem when locally testing an email link in a site I am building, I have since tried it on 'real' email links with the same result. Any ideas ? Is it Thunderbird or the way I have it setup ?