These error messages may occur if Microsoft Outlook or Microsoft Outlook
Express cannot establish a connection with your e-mail server. These error
messages are frequently caused by one of the following:
a.. You are not connected to the Internet or a network, or your mail
server is temporarily unavailable.
b.. Your account settings are incorrect.
c.. Your user profile in Outlook is damaged.
d.. An e-mail item on your POP3 server is damaged.
e.. The configuration of your AV software is incorrect.
f.. Outlook Express was removed from the computer or the installation is
damaged.
g.. The configuration of your personal firewall software is incorrect.
For further troubleshooting, please read here:
http://support.microsoft.com/kb/813514