Microsoft Outlook 2007

Open Outlook.
Select Tools > Account Settings from the menu at the top of the screen.
The Accounts window should appear and a list of email accounts should appear. Double-click on the email account that you would like to modify.
The E-mail Accounts window should appear. Click on the More Settings... button in the lower-right corner of the window.
The Internet E-mail Settings window should appear. Click on the tab that says Outgoing Server.
A checkbox with the words My outgoing server (SMTP) requires authentication will be at the top of the page. Make sure this checkbox is checked.
Directly below the checkbox is a circular radio button with the words Use same settings as my incoming mail server. Make sure this circle is selected and then click OK at the bottom of the page.
You will be returned to the E-mail Accounts window. Click the Next button at the bottom of the page.
Click Finish at the bottom of the Congratulations! page.