Have you checked your Outlook Express account lately? Just because you don't use it doesn't mean it hasn't been receiving mail. Junk e-mail/spam adds up over time and your space on the server could be full. That is where I would start. If it is empty, contact Verizon again.
I received a message from Verizon, my ISP, that I needed to empty my mailbox as it was almost full and would receive no new email soon. When I called to question this since I keep my email box emptied almost daily, I was told that Verizon does not support the email Mozilla and could not help me. Find it strange that my question is not about Mozilla but about the web mailbox of the ISP and their mail services. I want to set it up so that once I download an email it does not stay on the server thus avoiding an overloaded mailbox on the server, but since Verizon claims they do not support Mozilla, I could get no answers to my question. Is this going to be the usual service response by my using Mozilla instead of an email my ISP wants me to use which is Outlook Express and which I do not like?