Who is your ISP (aol, compuserve, earthlink, etc)?
Do you have messages in your Outbox?
If so, does deleting them help?
Are you using outlook or outlook express?
What do you have for the following settings?
Incoming Mail Server (POP3)
Outgoing Mail Server (SMTP)
In Outlook Express:
Select "Tools" on the top of the Outlook screen
Select "Account" from the drop down menu
Select the "Mail" Tab
Select your email account and click "Properties"
Select the "Servers" tab
In Outlook:
Select "Tools" on the top of the Outlook screen
Select "Email Accounts(may need to click arrows to get there)
Select View or Change Email Account and click 'Next'
Select your email account and click "Change"