Very interesting this thread.
I have Firefox set as my default browser on the desktop comp. on which I am at present typing. ( BT Broadband in use)) and it always opens with Firefox. However I do have a Laptop on which I have retained a 'dial-up' connection via Virgin.net and, as I have radio linked it to my main comp. it also opens automatically with Firefox and I can surf the net without any 'dial-up' connection. However, whilst all e/mails addressed to me via Virgin come through to the laptop without the 'dial-up' connection being involved, I do have reply, by a switching to 'dial-up' , in order to send a return message with my Virgin e/mail address.
I hope what I have said is understandable.
Ron