When I click on messenger email notifications it opens Windows Live mail, how do I change it to open email in hotmail (online)?

I used to click on 'email inbox new messages' icon in messenger and it would open a tab for hotmail, now it opens Windows Live Mail (which I hate) and I don't recall ever changing the settings.  I've looked everywhere to change the settings but can't find it, can anyone help.  I'm using Firefox browser.

Thanks