• Wrong username/password
• Wrong servernames
• Not connected to the internet
"Hang up after send/receive" is checked, kicking you offline each time you check email

Most of these problems can be fixed by opening outlook express, clicking on tools, then on accounts. You will then get this window. Highlight the appropriate account and click on properties.

On this window you have 5 tabs. The security tab you can disregard as well as advanced. The connection tab is rarely the problem but if you get disconnected after checking email and "hang up after send/receive" is NOT checked(see below), uncheck the box under connection.
The general tab looks like this. Name should be your name or whatever you want it to say when you send an email. Email address should be your email address. Reply address can be blank.

The servers tab looks like this. Make sure you have all the correct information entered. The mailservers are both mail.digitalil.net.

There are some other things you might want to change. These things could include automatically checking for mail every X amount of minutes, hanging up after send/receive, font sizes, allowing attachments to be opened, etc. These can all be found by clicking on tools, then options. Click through the tabs until you find something that you might be looking for. The most common problem for wanting to change anything in here has been displayed and circled.