Everytime i try logging it, it says my account is "over quota". I understand I have exceeded the 15MB limit, but what happens to incoming mail, will I not receive it? I have important email messages as well which I really don't want to delete. What can I do? Thanks

Forward your important emails to another email account that has a lot of space, like Gmail. You have to delete your emails and make space or you will not get new incoming emails.