Hey, I see this one alot. This is in Outlook express... In Outlook, click on the tools menu, then click on accounts. From here click on the mail tab (near the top of the Internet Accounts window). Now take a good look at your info in this screen. Mine says,
Account | Type | Connection
mail.tznet.com | mail(default) | Any Avalible
The last part is important, if yours says anything but any avalible under connection, that is your problem. So, you may ask, how do I fix this? Well, delete that account and readd it, that will set the connection to any avalible. Then you should be fine. There are other ways to change that if you don't know your email server names. If that is your prob and you need to know the other ways... just reply! Hope that helps!