Outlook Express will not connect with e-mail provider

When I click on my Outlook Express e-mail, my messages automatically begin downloading into my in box, until 2 days ago. Two days ago my ISP provider had an issue with e-mail, but claims the problem is fixed now.

The Problem: Now when I click on Outlook Express e-mail, I get a "Log on pop-up box" for my "log on server" asking me for my user name and password. Note: I've never had to log into my e-mail prior to my ISP provider "e-mail issue" 2 days ago. However, when I enter my user name and password, the window just pops-up again. I have contacted my ISP provider and they are able to get into my e-mail by entering my user name and password. They also reset my modem. But, I still cannot access my e-mail from my computer. Does anyone know what the fix is?

Thanks,