Lurker,
You can't. Welcome to the one thing ISP's can do to try to lock you in their control - people's reluctance to change their email address /ubbthreads/images/graemlins/xyxgun.gif
Everytime you switch from one ISP to another you will get a new email address, which is only valid in their mail servers. As long as they are the ones who control your mail, they can and will not let you keep using your email once you leave them.
I got tired of this BS many years ago and decided to use yahoo email instead. For about $10-20 per year I have a dedicated email account that will be active no mater what ISP I use.
So I use my yahoo email which is independent of my ISP. The ISP simply gives you a path to the internet - you don't have to ue their email.
If you do want to read email sent to your ISP email (upgrade notices, pricing increases, etc., that I am sure you want to get!), what you do is you go to your email settings (in your new ISP's email section) and simply forward all of your ISP email to your yahoo email - you will never miss one of their important emails /ubbthreads/images/graemlins/crackup.gif
Bottom line is that even with my "method", you still have to change email address. The point is that you change your email address ONCE AND FOR ALL. Then, anytime you get pissed at your ISP or want to try cable modem vs. DSL vs. ???, you can simply laught at your ISP /ubbthreads/images/graemlins/nana.gif and tell them "Hasta la vista, baby!" /ubbthreads/images/graemlins/wink2.gif
Will