Our servers do not relay outgoing email unless you request this from us. You need to use your internet service provider's mail relay for sending email. Configuring Outlook seems to cause some people a little difficulty. Note that the "Login Information" in the following screen refers to your incoming mail username and password.
To set up your outgoing server account details, the trick is to click the "More Settings" option, and then the "Outgoing Server" tab which allows you to set your outgoing username and password details:
Depending on your ISP's requirements, you may need to check "Require Secure Password Authentication".