Outlook Does Not Work

If you have installed or updated anti-virus software lately check to make sure it hasn't disabled Outlook.

Check these settings in Outlook:

Tools->E-mail Accounts
View or change existing e-mail accounts
Next
Select your ISP account and click Change

Verify all settings on the page, contact your ISP if you are unsure of any of them, this is likely where the problem is.

You can also check your 'pop' server settings.  For instance, mine are:
Incoming:  Pop.west.cox.net
outgoing:  Smtp.west.cox.net

First of all You need to check for pop, smtp servers for the email service provider, for ex for yahoo account pop server is pop.mail.yahoo.com & smtp server is smtp.mail.yahoo.com.
Then you need to check for incoming & outgoing ports & set them according to the email providers instructions.