You say that you can connect to the internet, but you're getting mail error messages - this could mean that you haven't configured Outlook Express correctly. You must enter a username and password, as well as the POP3 mailserver address before Outlook Express can connect to your inbound mail-server. You say that you've entered the server addresses, and they look OK to me, but have you entered a username ands password for each server? If you haven't, you'll be rejected.
A common cause of "cannot connect to the mail server" eror messages is that the computer is not actually online - people think they're connected when they're not. Can you access your ISP's webmail service, and read your email via Internet Explorer?
Confirm the situation with regards to the usernames/passwords, and we'll take it from there.